Utility of bortezomib retreatment in relapsed or refractory multiple myeloma patients: a multicenter case series.

Bortezomib therapy has become an important part of the standard of care for patients with relapsed multiple myeloma, and preliminary clinical evidence suggests that bortezomib retreatment in patients previously treated with the drug may prolong disease control. This retrospective study was designed to clarify the utility of bortezomib as a repeat therapy. We reviewed records from 3 major cancer centers that had participated in the phase II (SUMMIT or CREST) or phase III (APEX) registration studies to identify patients who were subsequently retreated off protocol with bortezomib-based therapy. We found 22 patients who received bortezomib retreatment following a 60 or more day gap between bortezomib treatments. Twelve patients had intervening therapy between initial bortezomib treatment and bortezomib retreatment. During retreatment, 14 of 22 patients received bortezomib in combination with another antineoplastic agent. The overall response rate for bortezomib retreatment was 50% (9% complete responses). The median length of retreatment was 5.1 months in responding patients and 2.4 months in nonresponding patients. Therapy was terminated due to unmanageable toxicity in 2 patients during retreatment, compared with 6 patients during initial treatment. During retreatment, no patients required dose reduction due to peripheral neuropathy, compared to 4 patients during their initial treatment. Thus, bortezomib retreatment appears to be safe and effective. Favorable observed response rates with bortezomib retreatment suggest that it may be a viable option for relapsed or refractory multiple myeloma, even in patients previously exposed to bortezomib.

An observational, retrospective analysis of retreatment with bortezomib for multiple myeloma.

PURPOSE: The aim of this retrospective chart review of patients with multiple myeloma (MM) was to describe patterns of retreatment with bortezomib-based therapy and responses to retreatment in a community-based setting. PATIENTS AND METHODS: Data were retrospectively extracted from the medical records of patients treated in US Oncology-affiliated community oncology clinics who received 2 separate treatments with bortezomib-based therapy. Eligible patients had > or = 60 days between treatments and > or = 4 bortezomib doses during initial treatment. Responses were determined primarily by laboratory values. Response categories included (1) very good partial response (VGPR), > or = 90% M-protein decrease; (2) partial response (PR), 50%-89% decrease; and (3) less than PR (< PR), < 50% decrease, excluding progressive disease (PD). RESULTS: Retreatment response data were available for 82 patients; 5 (6%) had VGPR, 12 (15%) had PR, 52 (63%) had < PR, 5 (6%) had PD, and 8 (10%) died. Among 62 patients with response assessments for initial treatment and retreatment, VGPR/PR rates to retreatment were 44%, 23%, and 13% among patients with VGPR, PR, and < PR to initial treatment, respectively. Median time between bortezomib treatments was 9.7 months; 29% of patients received non-bortezomib therapy between treatments. The most common treatment pattern (58% of patients) was single-agent bortezomib at initial treatment and retreatment. Toxicity contributed to discontinuation in 38% of patients during initial treatment and 22% during retreatment; rates of neuropathy contributing to discontinuation were 18% and 6%, respectively. CONCLUSION: Retreatment with bortezomib-based therapy is feasible, with predictable toxicities. This observational analysis supports bortezomib alone or in combination as a retreatment option after initial bortezomib treatment in patients with relapsed MM.