Retreatment with bortezomib alone or in combination for patients with multiple myeloma following an initial response to bortezomib.

This clinical trial was conducted to determine the safety and efficacy of bortezomib retreatment in patients with multiple myeloma (MM) who had previously responded to bortezomib. Patients with progressive MM who had previously tolerated bortezomib as a single agent or in combination with other drugs, with a minimum of partial response (PR; >or=50% M-protein reduction) for >or=4 months, who had not received intervening MM therapy, were retreated with bortezomib (days 1, 4, 8, and 11 of a 21-day cycle) with a starting dose being the dose at which the patient ended the initial treatment. Patients were allowed to receive bortezomib on retreatment in combination with dexamethasone, thalidomide, or doxorubicin. Thirty-two patients received bortezomib retreatment (most with added dexamethasone). The median treatment-free interval (last dose of initial bortezomib treatment to first dose of retreatment) was 9.9 (range 2.5-34.0) months. The median duration of retreatment was 2.8 (<1-7.9) months; median total duration of bortezomib treatment was 6.7 (2.5-19.8) months. Based on the investigators' assessment of best response, the overall response rate (complete plus PR) was 50%. The median time from start of retreatment to progressive disease (PD) was 6.6 (95% confidence interval: 5.1-9.6) months. Thirteen patients (41%) experienced PN; bortezomib-related SAEs were reported in four patients. Retreatment with bortezomib alone or in combination is effective and well tolerated in patients with MM who have responded to their initial bortezomib treatment.