Lenalidomide Plus Dexamethasone (Rev/Dex) in Newly Diagnosed Myeloma: Response to Therapy, Time to Progression, and Survival.

Background: We reported a high response rate with the combination of lenalidomide plus dexamethasone (Rev/Dex) as initial therapy for newly diagnosed multiple myeloma (Blood2005;106:4050–3). We now present new data on time to progression (TTP), progression free survival (PFS), and overall survival (OS) from this phase II trial, and also include updated response data. Patients and Methods: 34 patients (23 male and 11 female) were enrolled. Lenalidomide was given orally 25 mg daily on days 1–21 of a 28-day cycle. Dexamethasone was given orally at a dose of 40 mg daily on days 1–4, 9–12, 17–20 of each cycle. Patients were allowed to go off treatment after 4 cycles of therapy to pursue autologous stem cell transplantation (SCT), but treatment beyond four cycles was permitted at the physician’s discretion. For patients continuing therapy beyond 4 months, the dose of dexamethasone was reduced to 40 mg on days 1–4 of each cycle. Response was assessed by modified EBMT/International Myeloma Working Group Uniform Response criteria. All patients received aspirin (81 mg or 325 mg daily) as prophylaxis against DVT. Results: The median age was 64 years (range, 32–78). All patients were evaluable for response and toxicity. Median follow up is 21 months. Thirteen patients proceeded to SCT following initial therapy with Rev/Dex and were censored at that time point for purposes of calculation of response, TTP and PFS. Patients who discontinued therapy to proceed to SCT received a median of 4 cycles of therapy (range, 4–13), while those staying on Rev/Dex (n=21) received a median of 19 cycles of therapy (range, 2–30). Thirty-one of 34 patients (91%) achieved an objective response to therapy; including 6 patients (18%) achieving a complete response (CR) and 13 patients (38%) achieving very good partial response for a CR+VGPR rate of 56%. The CR+VGPR rate among the 21 patients staying on Rev/Dex as primary therapy without SCT was 67% (CR 24%, VGPR 43%). Median TTP, PFS, and OS have not been reached (Figure). By Kaplan-Meier method, the estimated 2 year progression rate was 18%. The 2-year PFS rate and OS rate were 74% and 91%, respectively. Fifty-five percent of patients experienced grade 3 or higher non-hematologic toxicity at any point during therapy, most commonly fatigue (21%), neutropenia (21%), anxiety (6%), pneumonitis (6%), muscle weakness (6%), and rash (6%). Two patients died on study: one attributed to infection unrelated to therapy, the patient had stopped all therapy for over a month before the fatal infection occurred; the other death was due to infection felt possibly related to therapy. One patient developed a pulmonary embolism (grade 4 toxicity), but recovered with therapy; no other patient developed deep vein thrombosis or pulmonary embolism. Conclusion: Rev/Dex is highly active and well tolerated in the treatment of newly diagnosed multiple myeloma with a high CR+VGPR rate of 56% for the trial, and 67% among the subset of patients receiving this regimen as primary therapy. Responses are durable with a low progression rate at 2 years.