Doublet Vs Triplet Lenalidomide-Containing Regimens in Newly Diagnosed Myeloma Patients, Younger or Older Than 75 Years: Subgroup Analysis of a Phase III Study

Introduction : a formal comparison between Lenalidomide-Dexamethasone (Rd) and Lenalidomide-Prednisone plus Melphalan (MPR) or Cyclophosphamide (CPR) has not been performed yet. We compared Rd vs. MPR vs. CPR in newly diagnosed multiple myeloma (NDMM) patients ≥65 years old in a multicenter phase III trial. Per protocol, upfront dose reductions of Dexamethasone, Melphalan and Cyclophosphamide were performed, according to patients age ( ≤75 years vs. >75 years). The primary endpoint was progression-free survival (PFS).

Methods : 662 patients with NDMM were randomized to receive nine 28-day cycles of Rd (n=222), MPR (n=218) or CPR (n=222). Rd: lenalidomide 25 mg/day for 21 days; dexamethasone 40 mg on days 1,8,15,22 in patients 65-75 years old and 20 mg in those >75 years; MPR: lenalidomide 10 mg/day for 21 days; melphalan orally 0.18 mg/Kg for 4 days in patients 65-75 years old and 0.13 mg/Kg in patients >75 years; prednisone 1.5 mg/Kg for 4 days; CPR: lenalidomide 25 mg/day for 21 days; cyclophosphamide orally 50 mg/day for 21 days in patients 65-75 years old and 50 mg every other day in patients >75 years; prednisone 25 mg every other day. After induction, patients were randomized to receive maintenance with lenalidomide alone (R) or with prednisone (RP).

Results : Patients characteristics were well balanced. Eighty-three (37%) patients in the Rd, 86 (39%) in the MPR and 80 (36%) in the CPR groups were older than 75 years. In intention to treat analysis, after a median follow-up of 31 months, no difference in PFS and overall survival (OS) was observed. Median PFS was 23 months in Rd, 27 months in MPR and 23 months in CPR (Rd vs MPR p=0.216; Rd vs CPR p=0.872; MPR vs CPR p=0.148). Median OS was not reached and was 73% in Rd, 67% in MPR and 72% in CPR at 3 years (Rd vs MPR p=0.663; Rd vs CPR p=0.754; MPR vs CPR p=0.448). A subgroup analysis, according to age was performed. No difference in response rate was observed. In patients ≤75 years, median PFS was 23 in Rd, 30 in MPR and 23 months in CPR (Rd vs MPR, p<0.04; Rd vs CPR p=0.897; MPR vs CPR, p<0.05).

Median OS was not reached and was 75% in Rd, 76% in MPR, 77% in CPR at 3 years (Rd vs MPR p=0.251; Rd vs CPR p=0.280; MPR vs CPR p=0.975). In patients >75 years, no PFS difference was noticed: median PFS was 22 in Rd, 18 in MPR, 21 months in CPR (Rd vs MPR p=0.572; Rd vs CPR p=0.699; MPR vs CPR p=0.914). An OS advantage was reported with Rd: median OS was not reached in Rd patients, and was 37 and 43 months in the MPR and CPR groups, respectively (Rd vs MPR p=0.04; Rd vs CPR p=0.430; MPR vs CPR p=0.323). The rate of at least one hematologic grade 3-4 adverse event was 29% in Rd, 66% in MPR, 33% in CPR patients ≤ 75 years and 29% in Rd, 70% in MPR, 33% in CPR patients > 75 years (MPR vs Rd/CPR p< 0.0001). No difference was observed in extra-hematologic adverse events: 25% in Rd, 24% in MPR and 25% in CPR patients ≤75 years; 29% in Rd, 35% in MPR, 34% in CPR patients >75 years.

Conclusion : this trial compared for the first time Rd, MPR and CPR in elderly NDMM. In all patients, the addition of alkylating agent to Lenalidomide-steroid combination did not show any advantage on PFS and OS. In a subgroup analysis, safety and efficacy data suggest that triplet regimens may be indicated in patients ≤75 years, while a doublet regimens for those >75 years. The MPR combination showed a PFS advantage in patients ≤75 years, with a higher incidence of hematologic toxicity and SPM. In patients >75 years an OS advantage was reported with Rd, mainly due to a higher efficacy of salvage treatments. Updated results will be presented at the meeting.