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Fall 2005 Volume 6, Issue 6:
IMF Hotline Coordinators Answer Your Questions
I have been diagnosed with a solitary plasmacytoma of the bone. What is it? And what is the likelihood that I will develop multiple myeloma?

The IMF Hotline 800-452-CURE (2873) is staffed by Nancy Baxter, Debbie Birns, and Paul Hewitt.
The phone lines are open Monday through Friday, 8am to 4pm (Pacific Time).
To submit your question online, please email TheIMF@myeloma.org.

Question: I have been diagnosed with a solitary plasmacytoma of the bone. What is it? And what is the likelihood that I will develop multiple myeloma?

Answer: A solitary plasmacytoma of the bone (SPB) is defined as a collection of malignant plasma cells found in a single location in the bone without evidence of disease elsewhere. If, in fact, you have a true SPB, your chances of cure with radiation (3500 cGy) therapy are quite good. When a patient is treated with attempted curative radiotherapy for a SPB and then goes on within a few years to develop multiple myeloma (MM), the major reason for this failure is that the patient had underlying MM all along and did not have a true SPB. Thus the failure was not that of the radiation therapy, but that the patient was not accurately diagnosed.

Diagnosis of SPB
In the past, it has been difficult to assess whether a patient who presents with what appears to be a SPB actually has some small or hidden amount of systemic myeloma. Blood work can determine the amount, if any, of the myeloma protein. A high amount of such protein would point towards the presence of MM. The term MM is used if there is, in addition to a plasmacytomata, an increase in plasma cells in the routine bone marrow. The patient should be checked for other relevant indicators of MM, such as low hemoglobin, elevated serum calcium, and elevated serum creatinine. Another important diagnostic factor is the presence or absence of other bone lesions. In the past, a skeletal survey was used to make this determination. However, negative skeletal surveys alone cannot rule out other bone lesions because such surveys are not sufficiently accurate. With MRI and/or FDG PET scanning, doctors can better determine if the patient has more wide-spread marrow involvement. The absence of such involvement after these more sensitive tests would give the doctor (and patient!) more confidence that there is no occult MM.

Adjuvant Therapy
Adjuvant therapy is a term used to describe additional therapy such as chemotherapy, steroids, thalidomide, or alpha-interferon after radiation. Studies done in the 1980s and 1990s evaluating the benefit of post-radiation therapy with various chemotherapies in an effort to reduce the chance of, or time to, new disease were inconclusive. The prevailing view at this time is that adjuvant chemotherapy should not be given for patients with SPB. However, bisphosphonate therapy can be considered to help heal the bone that was damaged by the plasmacytoma.

Even in the absence of adjuvant therapy for SPB, patients should be monitored regularly. It may take up to a year (or occasionally even longer) for the effects of the radiation therapy to be fully demonstrated in dropping monoclonal protein levels. During that time, you and your doctor should determine a schedule of visits every 2 or 3 months to evaluate your status. As time goes on, if you remain disease-free, this schedule can be lengthened to, for example, 4-6 month intervals. Such close monitoring will allow the doctor to find any sign of a recurrence or development of MM at an earlier point when treatment options are greater.

Likelihood of Curing SPB
As stated above, the important issue is accurate diagnosis. Local control of an SPB has been achieved in about 90% of cases. Disease-free survival of 10 years has been reported to be from 16% to 46%, depending on the study. This discrepancy is most likely a result of the fact that not all of the patients in each study had true SPBs, but rather had underlying MM. There have also been studies looking at what prognostic factors can be identified that will predict which patients will be cured and which patients will ultimately relapse and develop MM. The following factors have been identified in at least one study as increasing the likelihood of relapse: osteopenia (reduced bone density, perhaps indicating early evidence of MM), low levels of uninvolved immunoglobulins (again, this probably means the patient actually had occult MM at diagnosis), age over 60, and/or SPB on axial (head and trunk) skeleton region. In patients whose monoclonal protein persists after radiation therapy, the likelihood of relapse is greater; conversely, those whose monoclonal protein disappears after local radiotherapy are less likely to relapse.

Overall Outlook
As our understanding of how plasma cell cancers develop increases, and as our ability to accurately diagnosis and stage plasmacytomas and MM improves, doctors are better able to guide patients in making treatment decisions.

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