[Show abstract][Hide abstract] ABSTRACT: This multicenter phase 1/2 trial investigated the combination of bendamustine, lenalidomide, and dexamethasone in repeating 4-week cycles as treatment for relapsed refractory multiple myeloma (MM). Phase 1 established maximum tolerated dose (MTD). Phase 2 assessed overall response rate at the MTD. Secondary endpoints included progression-free survival (PFS) and overall survival (OS). A total of 29 evaluable patients were enrolled. Median age was 63 years (range, 38-80 years). Median number of prior therapies was 3 (range, 1-6). MTD was bendamustine 75 mg/m(2) (days 1 and 2), lenalidomide 10 mg (days 1-21), and dexamethasone 40 mg (weekly) of a 28-day cycle. Partial response rate was 52%, with very good partial response achieved in 24%, and minimal response in an additional 24% of patients. Median follow-up was 13 months; median OS has not been reached. One-year OS is 93% (95% confidence interval [CI], 59%-99%). Median PFS is 6.1 months (95% CI, 3.7-9.4 months) with one-year PFS of 20% (95% CI, 6%-41%). Grade 3/4 adverse events included neutropenia, thrombocytopenia, anemia, hyperglycemia, and fatigue. This first phase 1/2 trial testing bendamustine, lenalidomide, and dexamethasone as treatment of relapsed refractory MM was feasible and highly active. This study is registered at www.clinicaltrials.gov as #NCT01042704.