Antonio Palumbo, MD1*, Michel Delforge, MD, PhD2, John Catalano, MBBS, FRACP, FRCPA3, Roman Hajek, MD, PhD4, Martin Kropff, MD5, Maria Teresa Petrucci6*, Zhinuan Yu7*, Lindsey Herbein7*, Jay M. Mei, MD, PhD7, Christian J. Jacques, MD7 and Meletios A. Dimopoulos8
1University of Torino, Torino, Italy
2University Hospital Leuven, Leuven, Belgium
3Dorevitch Pathology Laboratory, Frankston Hospital, Frankston, Australia
4The Faculty Hospital Brno, Brno, Czech Republic
5University of Muenster, Muenster, Germany
6Università di Roma Sapienza, Rome, Italy
7Celgene Corporation, Summit, NJ
8Greek Myeloma Study Group, Athens, Greece
Lenalidomide is an oral IMiD® compound with a dual mechanism of action, namely tumoricidal and immunomodulatory activity, and has proven efficacy in patients with MM. The current study (MM-015) is a prospective, randomized phase 3 trial designed to evaluate the efficacy and safety of continuous lenalidomide treatment (MPR-R: melphalan, prednisone, and lenalidomide induction followed by lenalidomide maintenance) vs fixed-duration regimens of melphalan and prednisone (MP) or melphalan, prednisone, and lenalidomide (MPR) in transplant-ineligible patients with NDMM.
Methods: 459 patients aged > 65 years with NDMM, stratified by age and International Staging System (ISS) stage were randomized to receive MPR-R, MPR, or MP. During double-blind treatment, patients received melphalan 0.18 mg/kg (D1-4), prednisone 2 mg/kg (D1-4), with or without lenalidomide 10 mg/day (D1-21) for nine 28-day cycles. Following 9 cycles of MPR, patients received maintenance lenalidomide (10 mg/day; D1-21) or placebo until progression; MP patients received placebo until progression. Patients with progressive disease (PD) could enroll in the open-label extension phase (OLEP) and receive lenalidomide at 25 mg/day (D1-21) with or without dexamethasone at 40 mg/day (D1-4, 9-12, and 17-20). The primary comparison for this trial was MPR-R vs MP. Updated data from a pre-planned interim analysis at 70% of events (median follow-up of 21 months) are presented.
Results: MPR-R compared with MP resulted in a higher overall response rate (ORR; 77% vs 50%, P <.001) as well as higher rates of complete response (16% vs 4%, P < .001) and very good partial response (VGPR) or better (32% vs 12%,P < .001). Responses were more rapid in patients receiving MPR-R compared with MP (median 2 vs 3 months, P < .001), and improved over time. Overall, MPR-R reduced the risk of disease progression by 58% compared with MP (hazard ratio [HR] = 0.423, P < .001) with a higher 2-year progression-free survival (PFS) rate (55% vs 16%). PFS was extended in patients receiving continuous lenalidomide therapy vs fixed-duration MP regardless of gender, ISS stage (stage I/II vs III), kidney function (creatinine clearance > 60 vs < 60 mL/min), or baseline β2-microglobulin (< 5.5 vs > 5.5 mg/L). A landmark analysis comparing MPR-R and MPR initiated at the beginning of cycle 10 demonstrated that maintenance lenalidomide resulted in a 69% reduced risk of progression compared with placebo (HR = 0.314, P < .001). In addition, regardless of induction response (> VGPR or PR), patients who received maintenance lenalidomide had longer PFS compared with placebo. Importantly, patients relapsing during MPR-R had similar second-line treatment duration (median 55 weeks) compared with those relapsing while on placebo following MPR or MP (median 68 and 54 weeks, respectively). Additionally, PD rates during the OLEP were similar across all treatments (13% for each). Thus, outcomes of patients who relapse following continuous lenalidomide are similar to those who relapse following fixed-duration regimens, suggesting maintenance lenalidomide is not associated with more aggressive relapse. Follow-up remains too short to identify significant overall survival differences between the 3 groups.
MPR-R had a manageable safety profile with minimal cumulative toxicities. Discontinuation rates due to adverse events (AEs) for patients treated with MPR-R and MP were 20% and 8%, respectively. Grade 3/4 neutropenia, thrombocytopenia, and anemia occurred in 71%, 38%, and 24% of patients receiving MPR-R and 30%, 14%, and 17% of those receiving MP; no grade 3/4 peripheral neuropathy was observed. Importantly, maintenance lenalidomide was as well tolerated as placebo, with few grade 3/4 AEs. During maintenance, low rates of thrombocytopenia (3% vs 2%, respectively), neutropenia (2% vs 0%), deep vein thrombosis (1% vs 0%), and fatigue (1% vs 0%) were observed.
Conclusions: MPR-R achieved a higher ORR, as well as better quality and more rapid responses vs MP. Furthermore, MPR-R compared with fixed-duration regimens of MP and MPR resulted in an unprecedented reduction in the risk of progression with a manageable safety profile, and similar rates of PD in subsequent OLEP treatment. These data suggest that continuous lenalidomide therapy with MPR-R is superior to regimens of limited duration by providing sustained disease control in transplant-ineligible patients with NDMM.