Background: The combination of cyclophosphamide plus G-CSF has been the standard approach for autologous stem cell mobilization in Multiple Myeloma (MM) patients treated at MSKCC for many years. However with the recent FDA approval of plerixafor and its proven efficacy for stem cell collection in patients who had failed collection with cyclophosphamide and G-CSF, the use of plerixafor as first line agent has been advocated for patients with MM. Although proof of improved efficacy of such an approach over G-CSF/cyclophosphamide mobilization remains paramount, comparison of cost analysis between the 2 approaches is also an important parameter that needs to be considered before endorsing plerixafor as first line mobilization agent.
Study Design and Method: We performed a retrospective analysis of all MM patients treated between 11/2008 and 3/2011 who received either cyclophosphamide plus G-CSF or plerixafor plus G-CSF as first line mobilization regimen. During this period of time, the target number of stem cell collection was 10 x 106 stem cells/kg and patients collecting less than 4 x 106 stem cells/kg were considered mobilization failures and had a second attempt at stem cell mobilization using an alternative approach. Some patients received plerixafor as salvage regimen after failing cyclophosphamide mobilization, while others were re-challenged with a second cycle of plerixafor with cyclophosphamide and G-CSF after failing first line upfront plerixafor mobilization. Mobilization costs accounted for both groups included the costs associated with upfront mobilization, the second line mobilization in patients failing a first mobilization, as well as complications directly related to the mobilization procedures and consist of the following: Costs of drugs cyclophosphamide 3000 mg/m2, plerixafor 0.24 mg/kg, G-CSF 10 mcg/kg per dose administered prior and during pheresis sessions; hospitalization for cyclophosphamide administration; pheresis sessions; laboratory tests on pheresis days; and re-hospitalization occurring within 15 days of either mobilization approaches and considered directly related to the mobilization procedure. All costs were calculated using the institution’s ratio of cost to charges, and were normalized and adjusted based on institutional charges for 2010.
Results: Ninety-eight patients received cyclophosphamide and G-CSF while thirty-five patients received plerixafor as first line mobilization regimens. Eleven (11%) patients were readmitted due to cyclophosphamide complications, with an average hospital stay of 6.9 days, while none in the plerixafor arm was hospitalized. Twenty-one (21%) of the cyclophosphamide group failed mobilization and received plerixafor as salvage regimen of which 3 (3.1%) failed again and are considered ultimate failures. Two (6%) patients failed upfront mobilization with plerixafor and failed salvage mobilization and are considered ultimate failures (6%). The average number of pheresis sessions performed was 3.4 and 2.2 in the cyclophosphamide and plerixafor upfront groups respectively. In total the average cost per patient who received cyclophosphamide was 1.6 times greater than that of the patients who received plerixafor upfront.
Conclusion: This cost analysis indicates that the use of plerixafor upfront for stem cell mobilization may be more cost effective than the current widely used approach employing cyclophosphamide. The cost difference between the two approaches could be attributed to several factors: Cyclophosphamide mobilization requires an initial inpatient hospitalization in our institution and often results in re-admissions due to expected toxicity; additionally, the rate of failures, and therefore need for an additional salvage mobilization appears to be much higher with cyclophosphamide; upfront plerixafor was associated with fewer pheresis sessions, and reduced G-CSF use. As many institutions administer cyclophosphamide mobilization on an outpatient basis, it is important to note that the cost benefit of plerixafor upfront remains even if the hospitalization cost of cyclophosphamide mobilization is removed; the cost ratio of cyclophosphamide becomes 1.3 times that of plerixafor. Overall, this single institution study provides, in the context of current clinical practices at MSKCC, the rational for adopting the use of plerixafor as upfront mobilization agent in MM patients.