Reduced frequency treatment with bortezomib plus dexamethasone for elderly patients with relapsed and/or refractory multiple myeloma: a phase 2 study of the Japanese Myeloma Study Group (JMSG-0902).

Bortezomib is one of the most widely used novel drugs for the treatment of multiple myeloma (MM). However, twice-weekly intravenous administration is associated with innegligible adverse events and treatment discontinuation. We therefore evaluated the long-term efficacy and feasibility of reduced frequency treatment with intravenous bortezomib in elderly patients with relapsed and/or refractory MM. A total of 47 bortezomib-naïve patients (median age 75 years) received bortezomib (1.3 mg/m(2), intravenously) and dexamethasone (20 mg) on days 1, 8, and 15 of every 4-week cycle. Twenty-six patients completed the planned 8 cycles. Best responses were stringent complete response (sCR) in 5 patients, very good partial response (VGPR) in 3, PR in 15, stable disease (SD) in 18, and disease progression (PD) in 6, respectively. Median progression-free and overall survivals were 9.6 and 35.1 months, respectively. After progression, 11 patients were retreated with bortezomib-based regimens and another 24 patients with immunomodulatory drugs. Multivariate analysis revealed that ISS 3, t(4;14), and <4 therapy cycles were significantly poor prognostic factors and that subsequent therapy with bortezomib-based regimens was a favorable factor for extended OS. The common adverse events were diarrhea, constipation, and peripheral neuropathy with no grade 4 toxicity. In conclusion, reduced frequency treatment with intravenous bortezomib + dexamethasone is an effective option for elderly patients with MM.