Combination Therapy with Lenalidomide Plus Dexamethasone (Rev/Dex) for Newly Diagnosed Myeloma.

Purpose: Lenalidomide (CC-5013) is an analogue of thalidomide and a lead clinical compound in a new group of drugs called IMiDS® which have immunomodulatory properties. Lenalidomide has shown promising results in relapsed refractory myeloma. It has a markedly different side-effect profile compared to thalidomide, with significantly fewer non- hematologic adverse events; myelosuppression, especially neutropenia, is the most common toxicity. We report the results of a phase II trial using the combination of lenalidomide plus dexamethasone (Rev/Dex) as initial therapy for newly diagnosed multiple myeloma.

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 stem cell transplantation, 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. Objective response was defined as a decrease in serum monoclonal (M) protein by 50% or greater and a decrease in urine M protein by at least 90% or to a level less than 200 mg/24 hours, confirmed by two consecutive determinations at least 4 weeks apart. Sub-classification as very good partial response (VGPR) required in addition to criteria for partial response, >=90% reduction in serum M protein, 24 hour urine M protein less than or equal to 100 mg, and 5% or fewer plasma cells on bone marrow examination. 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. Thirty-one of 34 patients (91%) achieved an objective response to therapy, including 2 patients (6%) achieving a complete response (CR) and 11 patients (32%) achieving very good partial response. Of the 3 patients not achieving an objective response, two met criteria for minor response and one had stable disease. Responses were rapid; the median time to response was 1 month. Adequate stem cells (>3.0 million CD34 cells/kg body weight) were obtained in all patients who proceeded to autologous stem cell transplantation. Forty-seven percent of patients experienced grade 3 or higher non-hematologic toxicity, most commonly fatigue (15%), muscle weakness (6%), anxiety (6%), pneumonitis (6%) and rash (6%). One patient died on study, and this was attributed to infection unrelated to therapy; the patient had stopped all therapy for over a month before the fatal infection occurred. One patient developed a pulmonary embolism, 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 overall responses in over 90% of patients including complete and very good partial responses in 38%. Two large cooperative group trials are currently testing Rev/Dex as initial therapy for multiple myeloma in the United States.