Clinical outcome of bortezomib retreatment in patients with relapsed or refractory multiple myeloma.

This retrospective study investigated the clinical efficacy and safety of bortezomib retreatment in patients with relapsed or refractory multiple myeloma (MM). A total of 30 patients who relapsed or progressed after ≥6 months since the last dose of their previous bortezomib therapy were included in this study. During the median 6 cycles (range: 2-12) of bortezomib retreatment, 10 (33.3%), 2 (6.7%), and 6 (20.0%) patients achieved complete response, very good partial response, and partial response, respectively. Grade 3 or 4 neutropenia (47.0%), thrombocytopenia (43.0%), anemia (10.0%), and peripheral sensory neuropathy (3.0%) were observed. The median time to progression, progression-free survival, and overall survival were 5.8 months (95% CI: 2.6-9.0), 5.5 months (95% CI: 4.2-6.8), and 13.4 months (95% CI: 6.1-20.7), respectively. Patients who received bortezomib retreatment ≥12 months from initial last therapy had a 1-year OS rate of 65.8% (95% CI: 43.5-88.1) while patients receiving retreatment after 6-12 months interval had a 1-year OS rate of 41.7% (95% CI: 13.9-69.5) (P = 0.038). In conclusion, this study demonstrates that retreatment with bortezomib is an effective strategy for patients with MM who relapsed at a long interval after initial bortezomib therapy.