REVIEW:
International Myeloma Working Group guidelines for serum free
light chain analysis in multiple myeloma and related disorders
A. Dispenzieri1, R. Kyle1, G. Merlini2, JS Miguel3, H. Ludwig4, R. Hajek5, A. Palumbo6,
S. Jagannath7, J. Blade8, S. Lonial9, M. Dimopoulos10, R. Comenzo11, H. Einsele12, B. Barlogie13,
K. Anderson14, M. Gertz1, JL Harousseau15, M. Attal16, P. Tosi17, P. Sonneveld18, M.
Boccadoro6, G. Morgan19, P. Richardson14, O. Sezer20, MV Mateos3, M. Cavo21, D. Joshua22, I.
Turesson23, W. Chen24, K. Shimizu25, R. Powles26, S.V. Rajkumar1 and B.G.M. Durie27, on
behalf of the International Myeloma Working Group*
1Departments of Hematology/Laboratory Medicine/Pathology, Mayo Clinic, Rochester,
MN, USA; 2Department of Biochemistry, University Hospital San Matteo, Italy; 3Department of
Hematology, Servicio de Hepatología, Hospital Universitario de Salamanca. CIC, IBMCC
(USAL-CSIC). Spain; 41st Medical Department and Oncology, Wilhelminenspital Der Stat Wien,
Vienna, Austria; 5Czech Myeloma Group & Department of Internal Medicine Fn Brno and LF
MM Brno, Czech Republic, CR; 6Divisione de Ematologia, University of Torino, Torino, Italy;
7Department of Medical Oncology/Internal Medicine, St Vincent's Comprehensive Cancer
Center, New York, NY, USA; 8Department of Hematology, Hospital Clinic, IDIBAPS, Barcelona,
Spain; 9Hematology/Medical Oncology, Emory University, Atlanta, GA, USA; 10Departments of
Therapeutics, Alexandra Hospital, Athens, Greece; 11Department of Clinical Laboratories,
Memorial Sloan-Kettering Cancer Center, New York, NY, USA; 12Department of Internal
Medicine, University of Wurzburg, Wurzburg, Germany; 13Departments of Hematology and
Pathology, MIRT UAMS, Little Rock, Arkansas, USA ; 14Department of Medical
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Oncology/Hematologic Malignancies, DFCI, Boston, MA, USA; 15Department of Hematology,
Institute de Biologie, Nantes. France; 16Departments of Hematology and Biostatistics, Purpan
Hospital, Toulouse, France; 17Institute of Hematology and Medical Oncology, University of
Bologna, Bologna, Italy; 18Department of Hematology, Rotterdam, The Netherlands; 19
Department of Hematology/Oncology, The Leukemia and Myeloma Program, Wimbledon, UK;
20Department of Hematology/Oncology, University of Berlin, Germany, 21Institute of
Hematology and Medical Oncology Seragnoli, Bologna, Italy; 22Institute of Hematology, Royal
Prince Alfred Hospital, New South Wales, Australia; 23Department of Hematology/Medicine
Malmö University Hospital, Malmö, Sweden; 24Department of Hematology/OncologyBeijing
Chaoyang Hospital, Beijing, China; 25Department of Internal Medicine, Nagoya City Higashi
General Hospital, Nagoya, Japan; 26Department of Hematology/Oncology, Parkside Cancer
Centre, London, United Kingdom; and 27Aptium Oncology, Inc., Cedars-Sinai Outpatient Cancer
Center at the Samuel Oschin Comprehensive Cancer Institute, Los Angeles, CA, USA.
INVITED MANUSCRIPT: Leukemia Spotlight Series
Corresponding Author: Dr. Angela Dispenzieri
Associate Professor of Medicine
Division of Hematology and Division of Laboratory Medicine
Mayo Clinic
200 First Street SW
Rochester, MN 55905
United States of America
dispenzieri.angela@mayo.edu
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Phone: 507 284-2479
Fax: 507 266-4972
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Abstract
The serum immunoglobulin free light chain (FLC) assay measures levels of free and
immunoglobulin light chains. There are three major indications for the FLC assay in the
evaluation and management of multiple myeloma and related plasma cell disorders (PCD). In the
context of screening, the serum FLC assay in combination with serum protein electrophoresis
(PEL) and immunofixation yields high sensitivity, and negates the need for 24-hour urine studies
for diagnoses other than light chain amyloidosis (AL). Second, the baseline FLC measurement is
of major prognostic value in virtually every PCD. Third, the FLC assay allows for quantitative
monitoring of patients with oligosecretory PCD, including AL, oligosecretory myeloma, and
nearly two-thirds of patients who had previously been deemed to have non-secretory myeloma.
In AL patients, serial FLC measurements outperform PEL and immunofixation. In oligosecretory
myeloma patients, although not formally validated, serial FLC measurements reduce the need for
frequent bone marrow biopsies. In contrast, there are no data to support using FLC assay in place
of 24-hour urine PEL for monitoring or for serial measurements in PCD with measurable disease
by serum or urine PEL. This manuscript provides consensus guidelines for the use of this
important assay, in the diagnosis and management of clonal PCD.
Key words: Immunoglobulin free light chain; prognosis; myeloma; amyloid
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INTRODUCTION
The monoclonal plasmaproliferative disorders encompass a broad spectrum of diseases
ranging from the often benign monoclonal gammopathy of undetermined significance (MGUS)
to the potentially curable solitary plasmacytoma to the life-threatening conditions of multiple
myeloma (MM) and light chain amyloidosis (AL). For each of these diseases, measurements of
circulating monoclonal immunoglobulins have been the mainstay of diagnosis, prognosis and
management. Until the 1990s, the repertoire of tests to document and measure the monoclonal
immunoglobulins included electrophoresis (PEL), immunoelectrophoresis, immunofixation
electrophoresis (IFE), and nephelometric measurement of immunoglobulin heavy chains of
serum. For most MGUS and MM patients, these measurements appeared to be sufficient;
however, they were inadequate for the majority of patients with AL and more than the 3% of
myeloma patients with non-secretory or oligosecretory myeloma.
In the early 2000's an assay that measured serum immunoglobulin free light chains
(FLC) was developed.1 This assay differentiated itself from prior light chain reagents that were
called quantitative light chain measurements in that these novel polyclonal antibodies reacted
with only those epitopes that were hidden when bound to heavy chain but available when not
associated with heavy chain (Figure 1). As will be discussed, this assay has moved into clinical
practice based on the building evidence of its utility. The purpose of this document is to describe
its potential uses and most importantly distinguish which uses have proved utility and those
which are still undergoing investigation.
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IMMUNOGLOBULIN FREE LIGHT CHAIN PRODUCTION AND MEASUREMENT
Serum concentrations of FLC are dependent on the balance between production by
plasma cells and renal clearance. Serum FLC are cleared rapidly through the renal glomeruli with
a serum half-life of 2-4 hours and are then metabolized in the proximal tubules of the nephrons.
Under ordinary circumstances, little protein escapes to the urine, and serum FLC concentrations
have to increase manyfold before the absorption mechanisms are overwhelmed.2 Approximately
1030 g of FLC can be metabolized per day by the kidneys compared with normal plasma-cell
production of 0.51 g per day 3
Abnormal concentrations of and FLC may result from a number of clinical situations
including immune suppression, immune stimulation, reduced renal clearance, or monoclonal
plasma cell proliferative disorders. Sera from patients with either polyclonal
hypergammaglobulinemia or renal impairment often have elevated FLC and FLC due to
increased synthesis or reduced renal clearance respectively. The / FLC ratio (rFLC), however,
usually remains normal in these conditions.4 A significantly abnormal / rFLC should only be
due to a plasmaproliferative (or lymphoproliferative) disorder that secretes excess FLC and
disturbs the normal balance between and secretion.
SERUM FLC ASSAY
The serum FLC assay (FREELITETM, The Binding Site Ltd., Birmingham, U.K.) is based
on a commercial reagent set of polyclonal antibodies and is performed by immunonephelometry
and it can be performed on a number of automated laboratory instruments.1 The assay consists of
2 separate measurements: one to quantitate FLC and the other to quantitate FLC.
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Sensitive hemmagglutination assays showed reactivity to cells coated with the
appropriate FLC at dilutions of >1:16,000 and no reactivity to light chains contained in intact
immunoglobulin at dilutions of <1:2. Although this would suggest that the reagents have at least
a 10,000-fold difference in reactivity to FLC compared to light chain contained in intact
immunoglobulin,1 Nakano et al have shown that there is cross reactivity: 20% at an intact
immunoglobulin concentration of 12.5 mg/L for the reagent; and 0.35% at 50 mg/L for the
reagent.5 The greater the specificity, the better one's ability to quantitate and FLC in the
presence of a large excess of serum IgG, IgA and IgM. This distinction is important, because in
normal individuals and in the majority of patients with myeloma, most of the circulating light
chain is bound to heavy chains making less specific reagents a near surrogate for circulating
heavy chain measurement.
Katzmann et al defined the normal range using fresh and frozen sera from 127 healthy
donors 2162 years of age and frozen sera from 155 donors 5190 years of age from the serum
bank.4 The 95% reference interval for FLC was 3.319.4 mg/L, and that for FLC was 5.7
26.3 mg/L. For the / ratio, the 95% reference interval was 0.31.2, but it was decided that
diagnostic range should include 100% of donors, making the normal diagnostic range for FLC
/ 0.26 1.65. Using the 100% confidence interval increased the specificity of the test from
95% to 100%, with a drop in sensitivity from 98% to 97%. Patients with ratios greater than 1.65
contain excess FLC and are presumed to be producing clonal FLC. Patients with ratios less
than 0.26 contain excess FLC and are presumed to be producing clonal FLC.
The 100% confidence interval used reduces the likelihood that polyclonal activation of B-
cells will cause an abnormal ratio, but it is possible, and therefore the test must be interpreted in
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the context of clinical situation. If a patient is in the midst of an infection or a fare of a
rheumatologic condition, the test should be repeated at a later date.
Although the test is a major advance, it is not without its limitations..6 First, there can be
significant lot-to-lot variation (19-20% CV) between batches of polyclonal FLC antisera may
result in variable immunoreactivity of individual monoclonal FLCs and inconsistent results.6
Second, some monoclonal light chains (particularly FLC) do not dilute in a linear fashion and
may be underestimated in the absence of additional off line dilutions.6 Third, antigen excess can
cause falsely low serum FLC results with nephelometric techniques, and manual dilution may be
required for clinically suspicious samples.7 For large multi-institutional trials, serious
consideration should be had for running samples at a centralized testing facility that performs lot-
to-lot comparisons. Fourth, changes in amino acid sequence of the light chain may render certain
light chain epitopes unrecognizable to the FLC reagents, but apparent on immunofixation or even
electrophoresis. Conversely, extreme polymerization can cause an overestimation by as much as
10-fold.
URINE FLC ASSAY
Most typically, the quantity of urinary light chains has been measured by 24 hour urine
protein electrophoresis. One can measure urinary light chains by immunonephelometry as well,1
but this technique cannot be recommended routinely based on the present body of knowledge
regarding their use.8 Bradwell et al measured the free and concentrations in the urine of 66
normal individuals and found that the respective values are 5.4 ± 4.95 mg/L and 3.17 ± 3.3 mg/L
with a mean : ratio of 1:0.54 (95% confidence interval, 1:2.171:0.25).1 After studying urine
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specimens from 20 patients analyzed by Freelite (The Binding Site) and SDS-agarose gel
electrophoresis (Hydragel proteinurie, Sebia), Le Bricon et al concluded that when using the /
ratio the Freelite was more sensitive than electrophoresis to detect FLC, but that the
concentration was overestimated in 75% of cases.8 In another study of samples from patients
with LCMM, correlation between concentrations of FLC in serum and urine (measured by
immunoassay and corrected for urine dilution with creatinine concentrations) in the 224 patients
was non-existent (, r=0.29, p=0·001; , r=0.13, p=0.2).3 The urine immunoglobulin FLC test is
NOT recommended for monitoring patients.
ROLE OF THE SERUM FLC ASSAY IN DIAGNOSIS
Serum FLC Assay in Screening for Plasma Cell Disorders
It is clear that having excess involved FLC or an abnormal rFLC is common in
virtually all plasma cell disorders (Table 1). Historically, the gold standard for screening for PCD
has been PEL with immunofixation (IFE) of the serum and the urine. Important questions about
the FLC assay in terms of screening are: 1) does the FLC assay add anything to IFE; and 2) if the
tests are equivalent, is one test either cheaper or more convenient than the other? Neither of these
questions has been answered in full, but there are pertinent data. The most important screening
study was done by the Katzmann et al.9 They asked whether the serum immunoglobulin FLC
assay could replace urine IFE for screening patients suspected of having a monoclonal protein
related disorder. Within the Mayo Clinic plasma cell disorder data base, 428 patients who had a
positive urine IFE and who had serum PEL with IFE and serum FLC assay testing as a clinical
assessment were identified. Serum PEL with IFE alone would have missed the diagnosis in 28
patients (6.5%): MM (n=2); AL (n=19); plasmacytoma (n=3); smoldering MM (n=1); and
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MGUS (n=2).9 In contrast, serum FLC alone would have missed 14% of patients, but the
combination of serum IFE and FLC identified 99.5% of patients with a positive urine (Table 2).
The two patients, who would have been missed had the urine IFE not been done, had low risk
MGUS.9 These findings are similar to those found by Beetham et al, who reported that the
sensitivity and specificity of an abnormal serum rFLC as a single screening test to be 0.76 and
0.96 with negative and positive predictive values of 0.98 and 0.59, respectively.10 The FLC assay
at diagnosis is especially relevant in patients with AL amyloidosis or any disease that has
predominantly free light chains. Among 110 AL patients who had not been previously treated
and who had a FLC assay performed within 120 days of diagnosis, the rFLC was positive in 91%
compared with 69% for serum IFE and 83% for urine IFE. The combination of serum IFE and
serum FLC assay detected an abnormal result in 99% (109 of 110) of patients with AL.11
To date, there are no data that fully address what the FLC assay adds to the serum IFE,
although the Katzmann data come close.9 Its major deficiency in addressing this question is that the
population tested included patients with positive urine immunofixation studies; the chosen selection
criteria answered the question they posed, but increased the likelihood of a positive serum FLC
assay since the median amounts of serum FLCs required to produce overflow proteinuria has been
measured at 113mg/L for (range 7-39,500mg/L) and 278 mg/L for (range 6-710mg/L).12 There
are several papers that demonstrate that the addition of FLC to serum PEL or capillary zone
electrophoresis (CZE) increases the sensitivity of these tests, which is not surprising because they
only detect monoclonal proteins large enough to be seen through a normal or polyclonal
background. PEL and CZE should not be considered sufficient testing when contemplating a
diagnosis of plasma cell disorder. Typical sensitivity levels are 1-2 g/L for SPEP, 150-500mg/L for
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IFE and intermediate in sensitivity for CZE.1 Serum FLC immunoassays have a sensitivity of less
than 1 mg/L. 4
The conclusion drawn from these studies and others13-17 is that for the purpose of
screening for monoclonal proteins for all diagnoses except AL, the FLC can replace the 24 hour
urine IFE; however, once a diagnosis of monoclonal gammopathy is made, the 24 hour protein
IFE should be done. For AL screening, however, the urine IFE should still be done in addition to
the serum tests including the serum FLC.
Not only is the screening strategy of serum IFE and FLC sensible based on physiology,
but also potentially from a cost and practicality perspective. Katzmann et al. noted that the 2006
Medicare reimbursement for serum FLC analysis was $38 compared with $71 for 24 hour urine
studies (total protein, PEP and IFE).9 Hence, the cost of adding serum FLC analysis was
approximately half the cost of the comparable urine tests. In the study by Hill et al. in the UK,
there was an additional cost of $9 per patient to include the FLC assay. Since in many
laboratories the initial blood sample is accompanied by urine in only 40 to 52% of cases,10,13
there may be cost increases. Both patients and physicians are reluctant to do 24 hour urine
collections because of the inconvenience posed, but depending on the indication for the original
monoclonal protein study of the blood, they could be missing at least 10 -17% of cases with
either AL amyloidosis or light chain myeloma (LCMM) by doing serum IFE alone.11,15 The ease
of performing the FLC measurement could rectify this deficiency and lead to earlier diagnosis of
these disorders.
Recommendations for the use of the serum FLC assay in Screening: As shown in Table 4,
the serum FLC assay in combination with serum PEL and serum IFE is sufficient to screen
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for pathological monoclonal plasmaproliferative disorders other than AL, which requires
all the serum tests as well as the 24 hour urine IFE. If a diagnosis of a plasma cell disorder
is made, a 24 hour urine for PEL and IFE is essential for all patients.
PROGNOSTIC VALUE OF THE SERUM FLC ASSAY
The increased diagnostic sensitivity for the FLC diseases and the ability to eliminate
urine in the diagnostic screen was somewhat predictable once the analytic sensitivity of the
serum FLC assay was understood. A finding that emerged, but that was not entirely expected,
was that baseline values of serum FLC can be used for prognostication (Table3). The
pathogenic rationale for this linkage is not well understood, but one possibility is that higher
levels of FLC may be associated with IgH translocations 18 as well as increasing tumor
burden.19,20
Monoclonal Gammopathy of Undetermined Significance (MGUS)
Approximately 1/3 of MGUS patients have an abnormal rFLC and have a higher rate of
progression than those who do not (Figure 2A). Based on the size of the monoclonal protein
peak, the isotype of the heavy chain, and the rFLC, a risk model for progression of MGUS to
MM has been constructed.21 For the purpose of prognostic modeling, a rFLC of <0.25 or >4 was
selected as abnormal. In addition to abnormal rFLC, on multivariate modeling an M-spike
greater than or equal to 1.5 g/dL and a heavy chain isotype other than IgG were associated with
risk of progression to MM or related disorders. The risk of progression at 20 years for patients
with 0, 1, 2 or 3 risk factors was 5%, 21%, 37%, or 58%, respectively (Figure 2B).
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Smoldering (asymptomatic) multiple myeloma
In addition to the use of FLC for prognosis in MGUS, baseline rFLC is useful for
assessing prognosis for progression in smoldering MM.22 Baseline serum samples were available
in 273 patients with SMM seen from 1970 to 1995. Abnormal rFLC predicted for higher rates of
progression, and the best breakpoint for rFLC was less than or equal to 0.125 or greater than or
equal to 8 (hazard ratio, 2.3; 95% CI, 1.6-3.2) (Figure 2C). The extent of abnormality of rFLC
was independent of SMM risk categories defined by the number of bone marrow plasma cells
(BMPC) and size of serum M proteins.23 A risk model was constructed, incorporating the best
breakpoint of rFLC, BMPC 10%, and serum M protein 3 g/dL. Patients with 1, 2, or 3 risk
factors had 5-year progression rates of 25%, 51%, and 76% respectively (Figure 2D).
Solitary Plasmacytoma
In a cohort of 116 patients with solitary plasmacytoma the rFLC was retrospectively
determined on serum collected at time of diagnosis. An abnormal ratio was present in 47% and
associated with a higher risk of progression to myeloma (P = .039). The risk of progression at 5
years was 44% in patients with an abnormal serum rFLC at diagnosis compared with 26% in
those with a normal rFLC. One to 2 years following diagnosis, a persistent serum M protein level
of 0.5 g/dL or higher was an additional risk factor for progression to MM. A risk stratification
model was constructed using the 2 variables of rFLC (normal or abnormal) and M protein level
persistence at a level of 0.5 g/dL or greater. The low risk (n = 31), intermediate risk (n = 26), and
high risk (n = 18) groups had 5 year progression rates of 13%, 26%, and 62%, respectively (P
< .001).24
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Multiple Myeloma
Several studies have shown that baseline FLC is prognostic for survival in patients with
newly diagnosed active myeloma.20,25-27 Kyrtsonis et al found that in 94 MM patients rFLC was
prognostic (Figure 3A). Median baseline rFLC was 3.6 in -MM patients and 0.02 in -MM.
'High' rFLC (worse than median) correlated with elevated serum creatinine and lactate
dehydrogenase, extensive marrow infiltration and LCMM. The 5-year disease-specific survival
was 82% and 30% in patients with rFLC less extreme or more extreme than median, respectively
(P = 0.0001).25 The rFLC added to the international staging system (ISS), with ISS stage 3
patients having a 5 year disease specific survival of 52% versus 16% depending on their rFLC.
Van Rhee et al have also demonstrated that among 301 patients enrolled to receive total
therapy III, those with the highest levels of FLC-- greater than 750 mg/L, which was the highest
tercile--had the poorest outcomes (Figure 3B and C). The highest baseline FLC levels were
significantly associated with LCMM, elevated creatinine (greater than or equal to 176.8 microM
or 2 mg/dL), beta-2-microglobulin (greater than or equal to 297.5 nM/L or 3.5 mg/L), lactate
dehydrogenase (greater than or equal to 190 U/L), and bone marrow plasmacytosis higher than
30%.20
Lastly, Snozek et al have also shown in a cohort of 790 patients diagnosed with active
MM between 1995 and 1998 that baseline rFLC <0.03 or >32 (n=479) had inferior outcomes as
compared to those with an rFLC between 0.03-32 (n=311), with median survival of 30 versus 39
months, respectively.26 When the abnormal rFLC was incorporated into a model using the cut-
offs applied in the International Staging System,28 i.e. albumin <3.5 mg/dL and serum 2-
microglobulin 3.5 mg/dL, it was found that rFLC was an independent risk factor. Patients with
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0, 1, 2, or 3 adverse risk factors had significantly different overall survival, with median survival
times of 51, 39, 30 and 22 months, respectively, P<0.001 (Figure 3D).26
Immunoglobulin Light Chain Amyloidosis (AL)
In a cohort of 119 patients with AL undergoing peripheral blood stem cell transplantation,
there was a significantly higher risk of death in patients with higher baseline FLC (hazard ratio
2.6, P < .04).19 Baseline FLC correlated with serum cardiac troponin levels, and higher FLC
levels were associated with more organs involved by amyloid, suggesting that high FLC levels
may be associated with more advanced disease.
Recommendations for the use of the serum FLC assay in Prognosis: The serum FLC assay
should be measured at diagnosis for all patients with MGUS, smoldering or active multiple
myeloma, solitary plasmacytoma, and AL amyloidosis (Table 4).
ROLE OF THE FLC ASSAY IN RESPONSE ASSESSMENT
Although FLC response can be considered in 3 contexts--oligosecretory diseases, light
chain myeloma, and measurable intact immunoglobulin diseaseroutine serial use of this assay
can only be recommended for the first indication. As will be discussed below, to date there have
been only a few studies that have validated the usefulness of serial FLC measurements,19,29-31
although efforts for standardizing FLC response have been proposed.32,33 For serial
measurements, either the involved FLC or the difference between the involved and uninvolved
(dFLC) should be used.27 Aside from the time of diagnosis and in the context of documenting
stringent complete response, the rFLC is not useful because of the not infrequently observed
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treatment related immunosuppression of the uninvolved ( for monoclonal patients and for
monoclonal patients) FLC during chemotherapy; the ratios generated when one of the FLC
numbers is very low will be extreme, reflecting the degree of immunosuppression more than
tumor burden.
Published FLC response criteria (Table 5)
Multiple Myeloma: In MM, the International Myeloma Working Group has recently published
updated response criteria which incorporate the FLC assay. The criteria are shown in Table 5 as
they pertain to FLC. 33 There have been no formal studies performed yet to date to validate these
criteria.
AL amyloidosis: The consensus opinion from the 10th International Symposium on Amyloid and
Amyloidosis has defined FLC response in patients with AL amyloidosis as a FLC response in
those individuals in involved FLC (iFLC) greater than 10 mg/dL as a 50% reduction in iFLC and
progression as a 50% increase in iFLC.32 The definition used for amyloid patients has been
partially validated based on the work of Lachmann,29 Sanchorawala,31 and Palladini,30 as
described below.
Studies evaluating FLC response in oligosecretory disease (AL amyloidosis, oligosecretory
MM and light chain deposition disease)
Lachmann et al were the first to relate changes of FLC with overall survival in any
disease.29 They demonstrated that those AL patients who achieved more than a 50% reduction in
their iFLC were more likely to live longer. The majority of patients in that series were patients
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receiving non-myeloablative chemotherapy. Subsequently, in a group of patients undergoing
hematopoietic stem cell transplant (HSCT), Dispenzieri et al found that 50% reduction of iFLC
was not predictive of overall survival but that this degree of reduction was associated with a
trend toward improvement in both hematologic and organ response rate.19 Rather, normalization
of iFLC was the most important determinant to predict for hematologic response, organ response
and overall survival. In a study of 45 evaluable patients undergoing HSCT, Cohen et al
demonstrated that normalization of rFLC at 3 months predicted for both progression free and
overall survival.34 The discrepancy between the HSCT and non-transplant studies may lie in the
relative proportion achieving greater than a 50% reduction in iFLC. Contrary to the findings of
others, 19,31,34 reductions in iFLC greater than 50% did not further improve prognosis in the
Lachmann study.29 Sanchorwala and colleagues also demonstrated that the deeper the FLC
response, the higher likelihood of both organ and hematologic complete response.31 Moreover,
Palladini et al have shown that FLC reductions correlate with reductions of NT-proBNP, a
marker of cardiac function, and predict for overall survival.30 In the Sanchorwala series, greater
than a 90% reduction in serum FLC was a better predictor of organ response than was complete
hematologic response.31,35 Finally, Dispenzieri et al demonstrated that immunoglobulin FLC
response was a better predictor of survival in patients with AL amyloidosis than complete
hematologic response (Figure 4),19 as defined by the Blade myeloma response criteria.35
In contrast, there are no data to date to verify that FLC changes in patients with
oligosecretory myeloma correlates with those of bone marrow plasmacytosis or overall disease
status, but the assumption has been made that it does based on anecdotal information. 36 Six of
the patients studied during the course of their disease "showed changes in concentrations of FLC
that were in accordance with their clinical progress.36" Finally, although there are no published
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data validating the use of the FLC assay in patients with light chain deposition disease, the
personnel experience of the authors speaks to its utility in these cases.
Studies evaluating FLC response in light chain myeloma
There have been several studies that have demonstrated excellent sensitivity of the serum
FLC in detecting FLC in patients with LCMM. Consistently, however, it has been shown that
there is not a strong correlation between serum FLC and measurement or urine FLC by 24 hour
protein electrophoresis.3,12,27,37,38 When evaluating the performance of changes of serum FLC and
of urinary M-spikes over time, there is a relationship to the changes, but to date, no one has
shown high correlation coefficients.
Dispenzieri et al evaluated the relationship between serum FLC and 24-hour urine total
protein and 24 hour urine M-protein using 101 patients with baseline iFLC of 5 mg/dL or
greater. The correlation coefficients between percentage change of iFLC and urine M-protein
after 2 months of chemotherapy was poor.27 Smaller laboratory based studies have also been
performed. Abraham et al performed serial FLC measurements in 28 LCMM patients and used a
random effects model to estimate the correlation between changes in urinary M protein and
serum FLC. Changes in serum FLC over a period of time correlated with changes in the amount
of 24-h urinary M protein for an individual patient using a random effects model.37 Finally, when
Bradwell et al retrospectively reviewed screening baseline serum samples of 224 patients LCMM
who had enrolled onto MRC clinical trials, all were correctly identified from serum FLC
samples;3 however, upon serial monitoring of 82 of these patients, the authors observed "a
relationship" between responses as characterized by serum FLC and 24 hour urine PEL but do
not provide data about correlation coefficients and time points of the serial measurements.
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Role of FLC response in patients with measurable intact immunoglobulins
Monitoring of serum free-light-chains may eventually prove to be appropriate in
myeloma patients with intact immunoglobulin and those with LCMM, since approximately 95%
also produce excess serum FLC; 39 however, outside of measuring baseline levels, there are few
data to support this recommendation presently, with the exceptions noted below. One can parse
the possibilities into 3 categories: 1) using FLC response as an earlier predictor of overall
outcomes; 2) FLC response to define stringent complete response in myeloma; and 3) FLC to
replace urinary measurements, in the case of light chain escape.
It has been noted that measurements of serum FLC may be more sensitive for early
response and early relapse than are standard measurements of the involved heavy chain. With
regards to detecting early response or lack thereof, the rationale is logical. FLC half-life is 2-4
hours, whereas that for a typical IgG is approximately 8-21 days. Graphs have been presented
demonstrating this effect in patients.39 However, no one has shown that early detection of lack
of response predicts for ultimate treatment failure, or that the 3-4 week time delay that may occur
when using measurements of heavy chains actually affects the ultimate outcome of the patient.
Serial measurement of serum FLC may also detect relapse sooner than do the protein
electrophoresis studies. Once again, the difficulty lies in the absence of data to support that
knowledge of disease reactivation or drug failure a few months early has any impact on overall
patient outcome. Although the interesting argument has been made that earlier prediction of drug
failure could provide economic benefit in an era when novel agents are extremely expensive,40
there are not sufficient data to recommend abandonment of a treatment regimen based on the
FLC alone in patients with non-oligosecretory disease..
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Van Rhee et al reported that patients treated with VDT-PACE who had the deepest FLC
reductions after 2-3 cycles of therapy did worse than those who did not, but their analysis was
confounded by the fact that patients with lower levels of FLC were incapable of having very high
percentage reduction of their free light chains.20 For example a patient with a baseline FLC of 5
mg/dL cannot achieve a 96% reduction, which would be dropping the level to 0.2 mg/dL --a
pathologically low value. The authors provide no information about whether very high
percentages of reduction were independent of baseline FLC. In contrast, Dispenzieri et al
demonstrated that although FLC response at 2 months into alkylator based therapy predicted for
ultimate PEL response, it did not predict for overall or progression-free survival.27 The major
limitation of this study, however, is that the induction chemotherapy employed did not contain
novel chemotherapeutic agents.
Although normalization of rFLC has been incorporated into the definition of stringent
complete response in the International Myeloma Working Group Uniform Response Criteria,33
there are no data as of yet to document that complete response with or without the rFLC criteria
is prognostic for progression free survival or overall survival. There is one published study in
which patients were treated with doxorubicin and dexamethasone for 2 or 3 months followed by
thalidomide and dexamethasone for 2 months.41 The authors found that normalization of the
rFLC after one or two cycles of treatment, which occurred in 8 of 37 patients, was significantly
associated with the achievement of CR or nCR (P < 0.003). The significance of this finding is
uncertain because no information about PFS or OS as it related to rFLC normalization is
provided.
For those patients with intact immunoglobulin myeloma without significant Bence Jones
proteinuria, 24 hour protein electrophoresis is typically done infrequently. However, patients
Dispenzieri
20
with advanced disease can develop light chain escape with or without extramedullary disease.
For unclear reasons, a subclone of malignant plasma cells expands that is incapable of producing
significant amounts of immunoglobulin heavy chain, but retains the ability to make light chains.
Without doing periodic urinary evaluations or serum FLC measurements, this phenomenon can
be missed.42
Recommendations for the use of the serum FLC assay in Response Assessment: Serial FLC
ascertainment should be routinely performed in patients with AL amyloidosis and multiple
myeloma patients with oligosecretory disease. It should also be done in all patients who have
achieved a CR to determine whether they have attained a stringent CR.
USING THE FLC ASSAY IN THE SETTING OF RENAL INSUFFICIENCY
There is limited information about the use of this assay in the context of renal
insufficiency, but several generalizations are possible. Although renal failure will increase the
levels of both and FLC in a given individual, it will not cause an abnormal rFLC.
Interpreting serial measurements of iFLC in patients with oligosecretory myeloma, LCDD, or
amyloidosis who are on dialysis or who have markedly abnormal renal function is very
challenging, and response assessment has not been validated. However, following the dFLC or
the iFLC, whilst noting the uninvolved FLC and as an additional indicator of renal status, can
provide information in these very complicated patients.
CONCLUSION
In summary, there are four major indications for the FLC assay in the evaluation and
management of MM and related clonal plasma cell disorders. In the context of screening for the
Dispenzieri
21
presence of myeloma or related disorders, the serum FLC assay in combination with serum
protein electrophoresis and immunofixation yields high sensitivity, and negates the need for 24
hour urine studies when screening for multiple myeloma; once diagnosis of a plasma cell
disorder is made, 24 hour urine studies are required for all patients. Second, the FLC assay is of
major prognostic value in virtually every plasma cell disorder, including monoclonal
gammopathy of undetermined significance, smoldering myeloma, active myeloma,
immunoglobulin light chain amyloidosis (AL) and solitary plasmacytoma. Third, the FLC assay
allows for quantitative monitoring of patients with oligosecretory plasma cell disorders,
including patients with AL, oligosecretory myeloma, and nearly two-thirds of patients who had
previously been deemed to have non-secretory myeloma. In AL patients and patients with
oligosecretory myeloma, measurement of FLC is essential. The FLC assay cannot replace the 24
hour urine protein electrophoresis for monitoring myeloma patients with measurable urinary M-
proteins. Fourth, the rFLC a requirement for documenting stringent complete response according
the International Response Criteria.
Although the serum FLC is a valuable assay in patients with plasma cell disorders, there
are technical limitations of the assay which make its uses as a serial measurement potentially
problematic including: lot-to-lot variation; assay imprecision; and instances in which they do not
dilute in a linear fashion. The most important area for future investigation includes defining the
clinical relevance of early FLC "response" or "relapse" in patients with measurable intact serum
immunoglobulins or measurable urinary M proteins. Apart from initial diagnosis and
documentation of stringent complete response, its use is not advocated in these patients.
Dispenzieri
22
*International Myeloma Working Group:
Ray Alexanian, MD Anderson, Houston, Texas, USA
Kenneth Anderson, DFCI, Boston, Massachusetts, USA
Michael Attal, Purpan Hospital, Toulouse, France
Herve Avet-Loiseau, Institute de Biologie, Nantes, France
Ashraf Badros, University of Maryland, Baltimore, Maryland, USA
Leif Bergsagel, Mayo Clinic Scottsdale, Scottsdale, Arizona, USA
Joan Bladé, Hospital Clinica, Barcelona, Spain
Bart Barlogie, M.I.R.T. UAMS Little Rock, Arkanas, USA
Regis Batille, Institute de Biologie, Nantes, France
Meral Beksac, Ankara University, Ankara, Turkey
Andrew Belch, Cross Cancer Institute, Alberta,Canada
Bill Bensinger, Fred Hutchinson Cancer Center, Seattle, Washington, USA
Mario Boccadoro, University of Torino, Torino, Italy
Michele Cavo, Universita di Bologna, Bologna, Italy
Wen Ming Chen, MM Research Center of Beijing, Beijing, China
Tony Child, Leeds General Hospital, Leeds, United Kingdom
James Chim, Department of Medicine, Queen Mary Hospital, Hong Kong
Ray Comenzo, Memorial Sloane-Kettering, New York City, New York, USA
John Crowley, Cancer Research and Biostatistics, Seattle, Washington, USA
William Dalton, H. Lee Moffitt, Tampa, Florida, USA
Faith Davies, Royal Marsden Hospital, London, England
Cármino de Souza, Univeridade de Campinas, Caminas, Brazil
Dispenzieri
23
Michel Delforge, University Hospital Gasthuisberg, Leuven, Belgium
Meletios Dimipoulous, Alexandra Hospital, Athens, Greece
Angela Dispenzieri, Mayo Clinic, Rochester, Minnesota, USA
Hermann Einsele, Universitätsklinik Würzburg, Würzburg, Germany
Theirry Facon, Centre Hospitalier Regional Universitaire de Lille, Lille, France
Dorotea Fantl, Socieded Argentinade Hematolgia, Buenos Aires, Argentina
Jean-Paul Fermand, Hopitaux de Paris, Paris, France
Rafael Fonseca, Mayo Clinic Scottsdale, Scottsdale, Arizona, USA
Gosta Gahrton, Karolinska Institute for Medicine, Huddinge, Sweden
Morie Gertz, Mayo Clinic, Rochester, Minnesota, USA
John Gibson, Royal Prince Alfred Hospital, Sydney, Australia
Hartmut Goldschmidt, University Hospital Heidelberg, Heidelberg, Germany
Philip Greipp, Mayo Clinic, Rochester, Minnesota, USA
Roman Hajek, Brno University, Brno, Czech Republic
Izhar Hardan, Tel Aviv University, Tel Aviv, Israel
Jean-Luc Harousseau, Institute de Biologie, Nantes, France
Hiroyuki Hata, Kumamoto University Hospital, Kumamoto, Japan
Yutaka Hattori, Keio University School of Medicine, Tokyo, Japan
Joy Ho, Royal Prince Alfred Hospital, Sydney, Australia
Vania Hungria, Clinica San Germano, Sao Paolo, Brazil
Mohamad Hussein, Cleveland Clinic Taussig Cancer Center, Cleveland, Ohio, USA
Shinsuke Ida, Nagoya City University Medical School, Nagoya, Japan
Peter Jacobs, Constantiaberg Medi-Clinic, Plumstead, South Africa
Dispenzieri
24
Sundar Jagannath, St. Vincent's Comprehensive Cancer Center, New York, New York, USA
Hou Jian, Shanghai Chang Zheng Hospital, Shanghai, China
Douglas Joshua, Royal Prince Alfred Hospital, Sydney, Australia
Michio Kawano, Yamaguchi University, Ube, Japan
Shaji Kumar, Department of Hematology, Mayo Clinic, Minnesota, USA
Robert Kyle, Department of Laboratory Med. and Pathology, Mayo Clinic, Minnesota, USA
Juan Lahuerta, Grupo Espanol di Mieloma, Hospital Universitario, Madrid, Spain
Jae Hoon Lee, Gachon University Gil Hospital, Incheon, Korea
Henk Lokhorst, University Medical CenterUtrecht, Utrecht, The Netherlands
Heinz Ludwig, Wilhelminenspital Der Stat Wien, Vienna, Austria
Xavier LeLeu, Hospital Huriez, CHRU Lille, France
Angelo Maiolino, Rua fonte da Saudade, Rio de Janeiro, Brazil
Jayesh Mehta, Northwestern University, Chicago, Illinois, USA
GianPaolo Merlini, University of Pavia, Pavia, Italy
Philippe Moreau, University Hospital, Nantes, France
Gareth Morgan, Royal Marsden Hospital, London, England
Nikhil Munshi, Diane Farber Cancer Institute, Boston, Massachusetts, USA
Antonio Palumbo, Cathedra Ematologia, Torino, Italy
Santiago Pavlovsky, Fundaleu, Buenos Aires, Argentina
Ruben Niesvizky, Weill Medical College of Cornell University, New York, New York, USA
Yana Novis, Hospital SírioLibanês, Bela Vista, Brazil
Amara Nouel, Hospital Rutz y Paez, Bolivar, Venezuela
Raymond Powles, Leukaemia & Myeloma, Wimbledon, England
Dispenzieri
25
Linda Pilarski, University of Alberta, Alberta, Canada
S. Vincent Rajkumar, Mayo Clinic, Rochester, Minnesota, USA
Donna Reece, Princess Margaret, Toronto, Canada
Tony Reiman, Cross Cancer Institute, Alberta, Canada
Paul Richardson, Dana Farber Cancer Institute, Boston, Massachusetts, USA
Angelina Rodriquez Morales, Bonco Metro Politano de Sangre, Caracas, Venezuela
Orhan Sezer, Department of Hem/Onc, Universitatsklinikum Charite, Berlin, Germany
John Shaughnessy, M.I.R.T. UAMS, Little Rock, Arkansas, USA
Kazayuki Shimizu, Nagoya City Midori General Hospital, Nagoya, Japan
David Siegel, Hackensack, Cancer Center, Hackensack, New Jersey, USA
Guido Tricot, M.I.R.T. UAMS, Little Rock, Arkansas, USA
Jesus San Miguel, University of Salamanca, Salamanca, Spain
Seema Singhal, Northwestern University, Chicago, Illinois, USA
Pieter Sonneveld, Erasmus MC, Rotterdam, The Netherlands
Chaim Shustik, McGill, Toronto, Canada
Andrew Spencer, The Alfred Hospital, Melbourne, Australia
Keith Stewart, Mayo Clinic Scottsdale, Scottsdale, Arizona, USA
Patrizia Tosi, Italian Cooperative Group, Istituto di Ematologia Seragnoli, Bologna, Italy
Ingemar Turesson, Department of Hematology, Malmo University, Malmo, Sweden
Brian Van Ness, University of Minnesota, Minneapolis, Minnesota, USA
Ivan Van Riet, Brussels Vrija University, Brussels, Belgium
Robert Vescio, Cedars-Sinai Outpatient Cancer Center, Los Angeles, California, USA
David Vesole, St. Vincent's Comprehensive Cancer Center, New York, New York, USA
Dispenzieri
26
Anders Waage, University Hospital, Trondheim, Norway NSMG
Michael Wang, M.D. Anderson, Houston, Texas, USA
Donna Weber, MD Anderson, Houston, Texas, USA
Jan Westin, University of Lund, Lund, Sweden
Keith Wheatley, University of Birmingham, Birmingham, United Kingdom
Dina B. Yehuda, Department of Hematology, Hadassah University Hospital, Hadassah, Israel
Jeffrey Zonder, SWOG, Department of Hem/Onc., Karmanos Cancer Institute, Michigan, USA
Dispenzieri
27
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20. van Rhee F, Bolejack V, Hollmig K, Pineda-Roman M, Anaissie E, Epstein J, et al. High
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24. Dingli D, Kyle RA, Rajkumar SV, Nowakowski GS, Larson DR, Bida JP, et al.
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26. Snozek CL, Katzmann JA, Kyle RA, Dispenzieri A, Larson DR, Therneau TM, et al.
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staging system for multiple myeloma. J Clin Oncol 2005; 23:3412-3420.
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31. Sanchorawala V, Seldin DC, Magnani B, Skinner M, Wright DG. Serum free light-chain
responses after high-dose intravenous melphalan and autologous stem cell transplantation for
AL (primary) amyloidosis. Bone Marrow Transplant 2005; 36:597-600.
32. Gertz MA, Comenzo R, Falk RH, Fermand JP, Hazenberg BP, Hawkins PN, et al. Definition
of organ involvement and treatment response in immunoglobulin light chain amyloidosis
(AL): a consensus opinion from the 10th International Symposium on Amyloid and
Amyloidosis, Tours, France, 18-22 April 2004. Am J Hematol 2005; 79:319-328.
33. Durie BG, Harousseau JL, Miguel JS, Blade J, Barlogie B, Anderson K, et al. International
uniform response criteria for multiple myeloma. Leukemia 2006; 20:1467-1473.
34. Cohen AD, Zhou P, Chou J, Teruya-Feldstein J, Reich L, Hassoun H, et al. Risk-adapted
autologous stem cell transplantation with adjuvant dexamethasone +/- thalidomide for
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233.
35. Blade J, Samson D, Reece D, Apperley J, Bjorkstrand B, Gahrton G, et al. Criteria for
evaluating disease response and progression in patients with multiple myeloma treated by
high-dose therapy and haemopoietic stem cell transplantation. Myeloma Subcommittee of the
EBMT. European Group for Blood and Marrow Transplant. British Journal of Haematology
1998; 102:1115-1123.
36. Drayson M, Tang LX, Drew R, Mead GP, Carr-Smith H, Bradwell AR. Serum free light-
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37. Abraham RS, Clark RJ, Bryant SC, Lymp JF, Larson T, Kyle RA, et al. Correlation of serum
immunoglobulin free light chain quantification with urinary Bence Jones protein in light
chain myeloma. Clin Chem 2002; 48:655-657.
38. Singhal S, Stein R, Vickrey E, Mehta J. The serum-free light chain assay cannot replace 24-
hour urine protein estimation in patients with plasma cell dyscrasias. Blood 2007; 109:3611-
3612.
39. Mead GP, Carr-Smith HD, Drayson MT, Morgan GJ, Child JA, Bradwell AR. Serum free
light chains for monitoring multiple myeloma. Br J Haematol 2004; 126:348-354.
40. Hajek R, Cermakova Z, Pour L, Novontna H, Maisnar V, Tichy M, et al. Free light chain
assays for early detection of resistance to bortezomib-based regimens. Haematologica 2007;
92:93.
41. Hassoun H, Reich L, Klimek VM, Dhodapkar M, Cohen A, Kewalramani T, et al.
Doxorubicin and dexamethasone followed by thalidomide and dexamethasone is an effective
well tolerated initial therapy for multiple myeloma. Br J Haematol 2006; 132:155-161.
42. Dawson MA, Patil S, Spencer A. Extramedullary relapse of multiple myeloma associated
with a shift in secretion from intact immunoglobulin to light chains. Haematologica 2007;
92:143-144.
43. Abraham RS, Katzmann JA, Clark RJ, Bradwell AR, Kyle RA, Gertz MA. Quantitative
analysis of serum free light chains. A new marker for the diagnostic evaluation of primary
systemic amyloidosis. Am J Clin Pathol 2003; 119:274-278.
Dispenzieri
33
Figure Legends
Figure 1. Immunoglobulin free light chain assay.
A. Shows the location of the hidden light chain determinants in the intact immunoglobulin
model.
B. Shows the location of the hidden light chain determinants in the free light chain model.
Figure 2. Risk of progression to symptomatic myeloma or related disorder.
A. In 1148 patients with MGUS based on abnormal rFLC (<0.26 or >1.66). (Rajkumar SV, Kyle
RA, Therneau TM, et al. Serum free light chain ratio is an independent risk factor for
progression in monoclonal gammopathy of undetermined significance. Blood. 2005;106:812-
817).
B. In 1148 patients with MGUS using a risk-stratification model that incorporates rFLC and the
size and type of serum monoclonal protein. The 3 risk factors include: abnormal rFLC (<0.26
or >1.66); serum monoclonal protein of >=15g/L; and non-IgG MGUS. (Rajkumar SV, Kyle
RA, Therneau TM, et al. Serum free light chain ratio is an independent risk factor for
progression in monoclonal gammopathy of undetermined significance. Blood. 2005;106:812-
817).
C. In 273 patients with smoldering (asymptomatic) multiple myeloma based on rFLC <0.125 or
>8 (<1:8 or >8:1) (Dispenzieri A, Kyle RA, Katzmann JA, et al. Immunoglobulin free light
chain ratio is an independent risk factor for progression of smoldering (asymptomatic)
multiple myeloma. Blood. 2008;111:785-789).
Dispenzieri
34
D. In 273 patients with smoldering (asymptomatic) multiple myeloma using a risk-stratification
model that incorporates abnromal rFLC (<0.125 or >8), the size of serum monoclonal protein
(greater than or equal to 30 g/L)and extent of bone marrow plasmacytosis (greater than or
equal to 10%). (Dispenzieri A, Kyle RA, Katzmann JA, et al. Immunoglobulin free light chain
ratio is an independent risk factor for progression of smoldering (asymptomatic) multiple
myeloma. Blood. 2008;111:785-789).
Figure 3. Overall survival in patients with newly diagnosed symptomatic myeloma based
on baseline FLC measurement.
A. Overall survival based on rFLC thresholds in94 patients. `High rFLC' for patients with clonal
kappa or lambda disease was 3.6 and 0.02, respectively. (Kyrtsonis MC, Vassilakopoulos TP,
Kafasi N, et al. Prognostic value of serum free light chain ratio at diagnosis in multiple
myeloma. Br J Haematol. 2007;137:240-243.)
B. Overall survival based on baseline iFLC terciles in 301 patients undergoing Total Therapy 3.
Highest tercile (greater than 750 mg/L) was associated with worse overall survival (van Rhee
F, Bolejack V, Hollmig K, et al. High serum-free light chain levels and their rapid reduction in
response to therapy define an aggressive multiple myeloma subtype with poor prognosis.
Blood. 2007;110:827-832.)
C. Event free survival based on baseline iFLC terciles in 301 patients undergoing Total Therapy
3. Highest tercile (greater than 750 mg/L) was associated with worse overall survival (van
Rhee F, Bolejack V, Hollmig K, et al. High serum-free light chain levels and their rapid
reduction in response to therapy define an aggressive multiple myeloma subtype with poor
prognosis. Blood. 2007;110:827-832.)
Dispenzieri
35
D. Risk stratification model using elements of the international staging system (ISS) and extreme
values of rFLC adds in 790 patients diagnosed with active MM between 1995 and 1998.
Patients were assigned 1 point for each of the following: abnormal rFLC (<0.03 or >32); high
Sb2M (3.5 g/L); or low serum albumin (<3.5 g/dL). (Snozek CL, Katzmann JA, Kyle RA, et
al. Prognostic value of the serum free light chain ratio in patients with newly diagnosed
myeloma and proposed incorporation into the International Staging System Submitted.)
Figure 4. Free light chain response is a better predictor of overall survival than is
immunofixation electrophoresis response.
Dispenzieri A, Lacy MQ, Katzmann JA, et al. Absolute values of immunoglobulin free light
chains are prognostic in patients with primary systemic amyloidosis undergoing peripheral blood
stem cell transplantation. Blood. 2006;107:3378-3383.
Dispenzieri
36
Table 1. Rates of abnormal FLC ratio in different plasma cell disorders
Disease
n
Abn rFLC, %
Multiple myeloma (MM)
Symptomatic MM26
790
95
Symptomatic MM 39
456
96
Symptomatic MM 15
61
97
Symptomatic MM 27
399
96
Non secretory MM 36
28
68
Non secretory MM 11
5
100
Light chain MM3
224
100
Light chain MM37
28
100
Smoldering MM 11
72
88
Smoldering MM 22
273
90
MGUS 21
1148
33
MGUS 11
114
44
Amyloidosis 43
95
92
Amyloidosis29
262
98
Amyloidosis11
110
91
Light chain deposition disease11
28
93
FLC, immunoglobulin free light chain; rFLC, FLC ratio; Abn, abnormal; MGUS, monoclonal
gammopathy of undetermined significance
Dispenzieri
37
Table 2. Four-hundred and twenty-eight patients with urinary monoclonal protein detected
by immunofixation electrophoresis9
LABORATORY TEST
% ABNORMAL
Serum immunofixation electrophoresis
93.5
Serum protein electrophoresis
80.8
Serum FLC / ratio
85.7
Serum immunofixation electrophoresis or FLC ratio
99.5
Dispenzieri
38
Table 3. Technical limitations of the FLC assay.
Limitation
Comment
Lot to lot variability of reagent
Coefficient of variability ~10-20%
Antigen excess
Actual quantity can be drastically underestimated
Unrecognizable epitopes
Uncommon
Extreme polymerization
Uncommon
Dispenzieri
39
Table 4: Uses of serum immunoglobulin free light chain assay
SCREENING IN COMBINATION WITH IMMUNOFIXATION ELECTROPHORESIS9
BASELINE VALUES PROGNOSTIC
Monoclonal gammopathy of undermined significance21
Smoldering myeloma22
Symptomatic myeloma20,25-27
Plasmacytoma24
AL amyloidosis19
HEMATOLOGIC RESPONSE
AL amyloidosis19,29-32
"Non-secretory" myeloma*36
Stringent complete response in multiple myeloma*33
Light chain deposition disease (Personal experience of authors)
*Not yet validated
Dispenzieri
40
Table 5: Response Criteria for FLC32,33
Minimum to be
PR
CR
sCR
Progression
deemed measurable
AL32 without measurable1
50% reduction of
Normal rFLC & CR by
50% increase of
iFLC 100 mg/L
ND
serum or urine M protein
iFLC
IFE & bone marrow
iFLC to > 100 mg/L
AL32 with measurable1
ND
ND
ND
ND
ND
serum or urine M protein
MM33 without measurable1
iFLC 100 mg/L
50% reduction of
Normal rFLC & CR by
50% increase of
ND
serum or urine M protein
and rFLC abnormal
dFLC
IFE and bone marrow
dFLC
MM with measurable
Use of FLC not
Use of FLC not
Use of FLC not
Normal rFLC & CR by
Use of FLC not
disease27,33
recommended
recommended
recommended
IFE and bone marrow
recommended
iFLC, involved free light chain, i.e. for a patient with restricted disease and for a patient with restricted disease; dFLC,
difference between iFLC and uninvolved FLC; ND, not defined
1 Measurable M protein includes serum M-protein of at least 1 g/dL or a urine M-protein of at least 200 mg/24 hours for myeloma
patients (100 mg/24 hours for AL patients).
Dispenzieri
41
Figure 1
AB
Intact Immunoglobulin
Kappa
Free Light Chain
Exposed surface
Hidden surface
Previously
hidden
surface
Figure 2
Figure 3
Figure 4
Document Outline