LAUSR

8002 Background: High and comparable rates of MRD negativity were seen in NDMM pts after 4 28-day induction cycles with KRd followed by ASCT and 4 KRd consolidation (KRd_ASCT_KRd) and after 12 KRd cycles (KRd12), showing the superiority of both regimens over KCd induction-ASCT-KCd consolidation (KCd-ASCT-KCd) (Gay F ASH 2018). Here we evaluated the benefit of KRd_ASCT_KRd vs KRd12 in specific subgroups of pts. Methods: 474 NDMM pts ≤65 years were randomized to KRd_ASCT_KRd or KRd12 or KCd_ASCT_KCd. We compared rate of ≥VGPR, ≥CR, sCR, MRD negativity (centralized, second generation flow cytometry, sensitivity 10-5) after consolidation with KRd_ASCT_KRd vs KRd12 in patients with R-ISS 1 and R-ISS 2/3. Since high-risk pts may sometimes respond rapidly, but then relapse early, we also analyzed the rate of early relapse (<18 months from randomization). We performed a multivariate logistic regression analysis to evaluate factors predictive of early relapse. Results: Median follow-up was 25 months. Rates of ≥VGPR, ≥CR, sCR, MRD negativity were comparable between KRd_ASCT_KRd and KRd12 overall, in pts with R-ISS Stage 1 and with R-ISS Stage 2/3 (Table). A significantly lower number of pts experienced early relapse with KRd_ASCT_KRd vs KRd12 (12 pts [8%] vs 26 pts [17%]; P=0.015). This difference was mainly related to a significantly lower rate of early relapse in R-ISS Stage 2/3 pts receiving KRd_ASCT_KRd vs KRd12 (11 pts [12%] vs 22 pts [23%]; P=0.05); no difference was seen in R-ISS 1 (0 vs 2 pts). In multivariate regression analysis, KRd_ASCT_KRd vs KRd12 reduced the risk of early progression (OR 0.42; P=0.021); R-ISS Stage 2 (OR 3.6; P=0.001) and R-ISS Stage 3 (OR 4.85; P=0.003) increased the risk compared with R-ISS 1. Conclusions: KRd-ASCT-KRd and KRd12 were equally effective in inducing high-quality responses, with about 50% of high-risk pts achieving MRD negativity. In high-risk pts ASCT reduced the risk of early relapse. Clinical trial information: NCT02203643. [Table: see text]