Prospective evaluation of minimal residual disease in multiple myeloma following autologous stem cell transplantation(ASCT) and consolidation therapy.

e20033 Background: Induction therapy followed by autologous stem cell transplantation (ASCT) and maintenance therapy remains the standard approach in multiple myeloma (MM). The definitive role of consolidation therapy after ASCT is not known. We prospectively studied the impact of 2 cycles of Bortezomib, lenalidomide, and dexamethasone (RVd) consolidation therapy on minimal residual disease (MRD) in patients with MM post ASCT. Methods: Between June 2016 and July 2017,forty six patients were screened; of these 41 patients were recruited on day +100 post ASCT. Median age was 52 years (range, 32 to 66 years), 63.4% were males. 56% had ISS stage III and 36.6% had the extramedullary disease. 28% had received 2 lines of therapy prior to ASCT. Pre-transplant 85.4% patients had chemosensitive disease (CR 36.6%; VGPR 24.4%; PR 24.4%). Patients had received high dose melphalan 200 mg/m2 for conditioning. Patients received two cycles (q28days) of bortezomib (1.3mg/m2 weekly subcutaneously), lenalidomide (15mg/day orally for 15days), and dexamethasone 40 mg once a week as consolidation. The primary objective was response rate after consolidation therapy. Secondary objectives were MRD negativity, progression-free survival (PFS) and toxicity of consolidation therapy. MRD assessment was done with multi-parametric flow cytometry with a sensitivity of 0.001%. Response assessment was done as per the IMWG response criteria. Results: Post ASCT, 78% patients attained CR, 17.1% VGPR and 4.9% PR. Post-consolidation; CR rate increased to 95%. MRD negativity rate on day 100 post-ASCT and post two cycles of consolidation was 52.5% and 77.5%, respectively.At a median follow up of 11 months, median PFS and OS have not reached. Estimated one-year PFS and OS is 87% and 94% respectively. Five patients relapsed post consolidation with a median time of 14.7 months (range: 6.9 to18.6 months). Three of 5 patients were MRD positive post-consolidation. Day 100 and post-consolidation MRD positivity was more in the relapsed cohort. (p = 0.01 and p = 0.006 respectively) Conclusions: Consolidation therapy with two cycles of RVd improves response rate and MRD negativity rate post-ASCT. Clinical trial information: CTRI/2017/06/008741.