Combination of Lenalidomide, Melphalan, Prednisone and Thalidomide (RMPT) in Relapsed/Refractory Multiple Myeloma: Results of a Multicenter Phase II Clinical Trial

Background: In newly diagnosed multiple myeloma (MM) patients the addition of lenalidomide or thalidomide or bortezomib to the standard oral melphalan and prednisone (MP) combination significantly increased response rate and event-free survival. In advanced MM, the 4 drug combination VMPT further improves response rate. In this multicenter open label phase I/II trial the safety/efficacy profile of the 4 drug combination, lenalidomide, melphalan, prednisone and thalidomide (RMPT) was evaluated in patients with relapsed/refractory myeloma.

Methods: Oral lenalidomide was administered at 10 mg/day on days 1–21, oral melphalan at 0.18 mg/kg on days 1–4, oral prednisone at 2 mg/kg on days 1–4. Thalidomide was administered at 50 mg/day (Arm A) or 100 mg/day (Arm B) on days 1–28. Each course was repeated every 28 days for a total of 6 courses. Aspirin 100 mg/day was given as a prophylaxis for thrombosis. Maintenance therapy included lenalidomide alone at 10 mg/day on days 1–21.

Results: Forthy-four patients, median age 69 years (range 47–80), with relapsed or refractory MM were enrolled. Twenty-six patients received RMPT as second line of therapy, 18 as third line. Twenty patients received prior autologous transplant, 10 thalidomide-based regimen, 9 bortezomib-based regimen and 3 allogeneic stem cell transplant. After a median of 2 courses, 75.8% of patients achieved at least a partial response (PR), including 30% very good partial response (VGPR). Among patients who received RMPT as second line therapy the PR rate was 81.8%, including VGPR 36.4%.Among patients who received thalidomide 100 mg, the PR rate was 93.3% (including VGPR 46.7%) compared to 64.7% of thalidomide 50 mg. The 1-year-progressionfree survival was 48.6% and the 1-year survival from study entry was 90%. Grade 3–4 hematologic adverse events included: neutropenia (66.6%), thrombocytopenia (36.3%) and anemia (30.2%). Grade 3–4 non hematologic adverse events included: infections (21.2%), neurological toxicity (6%) and fatigue (9%). No thromboembolic events were reported.

Conclusion: Initial results showed that RMPT is an effective salvage therapy with a high proportion of responses. Toxicities were manageable. No thromboembolic complications were reported.