BACKGROUNDAlthough previous clinical study revealed that bortezomib combined with dexamethasone had improved the outcomes of relapsed or refractory multiple myeloma (RRMM), the optimal dose combinations of bortezomib and dexamethasone remain unknown. This trial aimed to observe the efficacy and safety of different dose combinations of bortezomib and dexamethasone in the treatment of RRMM patients in China.

METHODSA total of 168 patients with relapsed multiple myeloma (MM) who were refractory to at lest two prior treatments were enrolled in this multicenter, open-label, non-randomized, prospective clinical trial. Twenty patients received 1.3 mg/m(2) of bortezomib twice weekly for 2 weeks of a 3-week cycle for up to 8 cycles and oral or intravenous dexamethasone 20 mg on the day of and after each bortezomib dose (group 1); 66 patients received less than 1.3 mg/m(2) (0.7 - 1.0 mg/m(2)) of bortezomib and dexamethasone 20 mg on the same schedule (group 2); 37 patients received 1.3 mg/m(2)2 of bortezomib and dexamethasone 40 mg (group 3) and 45 patients received less than 1.3 mg/m(2) (0.7 - 1.0 mg/m(2)) of bortezomib and dexamethasone 40 mg (group 4). The response was evaluated according to the criteria of the European Group for Blood and Marrow Transplantation and confirmed by an independent review committee. Adverse events were graded according to the National Cancer Institute Common Toxicity Criteria, version 3.0.

RESULTSThe median age of groups 1 to 4 was 61, 62, 56, and 60 years, respectively. Most patients were in stages II/III of MM and the most common subtype was IgG. The rate of overall response to bortezomib and dexamethasone of group 1 to 4 was 72.2% (13/18), 73.8% (48/65), 78.8% (26/33) and 78.0% (32/41) (P = 0.91), including a complete response rate of 22.2% (4/18), 20.0% (13/65), 33.3% (11/33) and 29.3% (12/41) (P = 0.67), respectively. There was no statistical significance in time to progression and overall survival among these 4 groups (P > 0.05). The most commonly adverse events of any grade in the entire 4 groups were fatigue, gastrointestinal effects, peripheral neuropathy and thrombocytopenia, and there was no significance in the number of adverse events among the 4 groups (P > 0.05) except that peripheral neuropathy was reported more frequently in group 3 (36.3%) than in group 2 (13.8%, P < 0.05) and group 4 (14.6%, P < 0.05).

CONCLUSIONSThe combination of bortezomib and dexamethasone was associated with high responses in Chinese RRMM patients. No significant differences of efficacy were detected in different dose combinations of bortezomib and dexamethasone. Moreover, low dose of bortezomib reduced the incidence of peripheral neuropathy without affecting outcome in the treatment of patients with RRMM in China.