The addition of dexamethasone to bortezomib for patients with relapsed multiple myeloma improves outcome but ongoing maintenance therapy has minimal benefit

Despite the common practice of combining dexamethasone (Dex) with bortezomib (Bz) in patients with multiple myeloma (MM), until now there has been few prospective trials undertaken. We undertook a trial that recapitulated the original APEX study except that dexamethasone was incorporated from cycle 1. We also incorporated an exploratory maintenance component to the study. Twenty sites enrolled 100 relapsed/or refractory MM patients utilizing eight 21 day cycles of IV Bz [1.3 mg/m2; Day (D) 1, 4, 8, 11] and three 35 day cycles; Bz (1.3 mg/m2; Day (D) 1, 8, 15, 22). Our study was registered at www.clinicaltrials.gov (NCT00335348). Patients with stable disease or better received maintenance Bz (1.3 mg/m2) every 14 days until progression. Dexamethasone (20 mg) was given for 2 days with each Bz dose. A prospectively defined matched-analysis of primary (overall response rate; ORR) and secondary endpoints [Complete Response (CR) and time to progression (TTP)] compared our cohort to those on the Bz arm of the APEX trial. The addition of Dex improved ORR by 20% (56% vs. 36%) [odds ratio 0.44 (0.24-0.80)]. The median TTP was also significantly longer (10.1 vs. 5.1 months) (hazard ratio 0.50, 95% CI: 0.35-0.72, P=0.0002) and our landmark analysis demonstrated that this was largely due to the early use of dexamethasone, as we were unable to demonstrate any benefit of bortezomib/dexamethasone maintenance therapy.