PROLONGED MOLECULAR AND CLINICAL REMISSIONS IN FOLLICULAR LYMPHOMA PATIENTS TREATED WITH HDT/ASCT AND COMBINATION IMMUNOTHERAPY WITH RITUXIMAB AND INTERFERON α

Introduction: Follicular lymphoma is an indolent disease with a relapsing remitting course and shorter remission periods with each successive treatment. The median PFS and OS for patients who relapse within 12 m of prior therapy are 13 m and 60 m, respectively. Strategies to improve outcome including combining autologous stem cell transplant (ASCT) with effective immunotherapies such as rituximab (R) and/or interferon α (IFN α) could be considered. Detailed long-term data, including impact of minimal residual disease (MRD) status on PFS, are lacking for combination approaches such as this. We present long-term follow-up of a median 10 y of PFS and MRD on a cohort of 30 patients who received ASCT followed by maintenance R-IFN α. Methods: Patients in 1st or 2nd relapse were enrolled in this prospective study. Salvage included CHOP or DHAP with 3 weekly infusions of R prior to stem cell harvest as an “in vivo purge”. Patients then received high-dose therapy with cyclophosphamide, BCNU and etoposide followed by ASCT. IFN α began at 3-m post ASCT for 2 y with 6 weekly infusions of R from week 14. Response assessment included clinical, radiographic, and MRD assessments of bone marrow (BM) and peripheral blood (PB). Real-time quantitative PCR was used to evaluate MRD on the apheresis product and on BM and PB Q3m post ASCT for 1 y and Q6m from then on. An extended follow-up study included MRD assessment on patients who remained in CR. Results: From July 2000 to September 2009, 36 patients were enrolled with a mean age of 47 y (30–66 y). Sixty-seven percent of patients had stage IV disease, 50% had a FLIPI score of 3 or 4, and the median time from previous chemotherapy to enrolment was 12.8 m. Six patients were not transplanted. The median follow-up was 124 m (range 23–194 m), the 10-y OS and EFS was 69% and 40%, respectively, in the ITT population, and 50% and 56% in the SCT group. There was evidence of plateau at 100-m post ASCT. Seven transplanted patients died: 4 from progressive disease and 3 from secondary malignancies. Of the 30 transplanted, there were PCR markers for 22 (73%). Although 10/22 (45%) stem cell collections were MRD+, PFS was not significantly different from patients transplanted with MRD− grafts. Clinical and molecular remission in PB was achieved after R-IFN in 5 of 7 patients who were MRD positive in the BM at 3-m post ASCT. Both of these results suggest that R-IFN may be effective in eradicating MRD post ASCT. There appears to be good correlation between MRD assessment on PB and clinical response/relapse (Figure 1). Fifteen patients reached 100-m EFS, and of these, 9 PCR evaluable patients were also in molecular remission. Uni- and multi-variate analyses were performed. Keywords: autologous stem cell transplantation (ASCT); follicular lymphoma (FL); minimal residual disease (MRD).

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