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Introduction:
Although, rituximab containing chemotherapy regimens have improved response rates in B-cell lymphomas, a significant percentage of patients will eventually relapse. Autologous stem cell transplantation (Auto SCT) may provide long term remission in some of these patients. Tumor contamination of harvested stem cell graft has been postulated as a reason for relapse after Auto SCT. Single agent rituximab has been used for in-vivo purging of CD20+ tumor cells with positive results. In this study, we aimed to evaluate whether use of rituximab based in-vivo purging is still beneficial in the era of universal use of rituximab containing chemotherapy in patients with follicular (FL) or mantle cell lymphoma (MCL).
Materials and Methods:
Twenty consecutive patients with a diagnosis of relapsed CD20+ FL or transplant eligible MCL were included in this study. All patients received rituximab containing chemotherapy. Restaging was done after completion of chemotherapy and those with chemo-sensitive disease (n=14) were considered for Auto SCT. Polymerase Chain Reaction (PCR) analysis for bcl2 and bcl1 were done on apheresis products from patients with FL and MCL respectively. In-vivo purging with single agent rituximab was planned if any stem cell product were to be found PCR positive prior to Auto SCT.
Results:
A total of 19 patients were eligible for analysis. Patient characteristics are shown in the accompanying table. The bcl-2/bcl-1 status of the graft was available in 14 patients (FL; n=10 and MCL; n=4). The stem cell products in all 14 patients tested negative by PCR for both bcl2 (FL) and bcl1(MCL). None of these patients required additional rituximab treatment for in-vivo purging. Eleven patients (FL; n=7 and MCL; n=4) underwent Auto SCT. Three Patients with FL opted for ‘Harvest and Hold' approach and delayed transplantation. Median (range) PFS and OS of patients with FL undergoing Auto SCT were 2 yrs. (9 mo-5 y) and 3 yrs. (2-5 y) and those with MCL were 3 yrs. (2-4y) and 4 yrs. (2-5 y) respectively (median duration of follow up-3yrs.).
Discussion:
In this small cohort of patients with FL and MCL treated by R-chemotherapy, 100% of the harvested stem cell products were tumor free by PCR analysis. Our findings suggest that with universal use of rituximab containing chemo-immunotherapy in patients with FL and MCL, additional in-vivo purging may not be required. We may also conclude that persistence of residual/refractory disease after auto SCT rather than tumor contamination of the graft was the most likely cause of relapse in this cohort.
Table 1: Patient Characteristics
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