A phase 2 study of three low-dose intensity subcutaneous bortezomib regimens in elderly frail patients with untreated multiple myeloma

This phase 2 trial evaluated three low-dose intensity subcutaneous bortezomib-based treatments in patients ≥75 years with newly diagnosed multiple myeloma (MM). Patients received subcutaneous bortezomib plus oral prednisone (VP, N=51) or VP plus cyclophosphamide (VCP, N=51) or VP plus melphalan (VMP, N=50), followed by bortezomib maintenance, and half of the patients were frail. Response rate was 64% with VP, 67% with VCP and 86% with VMP, and very good partial response rate or better was 26%, 28.5% and 49%, respectively. Median progression-free survival was 14.0, 15.2 and 17.1 months, and 2-year OS was 60%, 70% and 76% in VP, VCP, VMP, respectively. At least one drug-related grade ≥3 non-hematologic adverse event (AE) occurred in 22% of VP, 37% of VCP and 33% of VMP patients; the discontinuation rate for AEs was 12%, 14% and 20%, and the 6-month rate of toxicity-related deaths was 4%, 4% and 8%, respectively. The most common grade ≥3 AEs included infections (8-20%), and constitutional (10-14%) and cardiovascular events (4-12%); peripheral neuropathy was limited (4-6%). Bortezomib maintenance was effective and feasible. VP, VCP and VMP regimens demonstrated no substantial difference. Yet, toxicity was higher with VMP, suggesting that a two-drug combination followed by maintenance should be preferred in frail patients .