Randomized controlled trials in relapsed/refractory chronic lymphocytic leukemia: a systematic review and...

This systematic literature review with meta-analysis was conducted on the clinical efficacy and safety of interventions used in the treatment of chronic lymphocytic leukemia (CLL). We systematically searched databases (PubMed, Cochrane Library, and Embase; 1997 to August 2, 2012), conference abstracts, bibliographic reference lists, recent reviews, and Clinicaltrials.gov. Primary efficacy outcomes were objective response rate, progression-free survival, and overall survival. Safety end points were Grade 3/4 toxicities, serious adverse events, withdrawals because of toxicity, and deaths due to toxicity. Studies were selected if they were randomized controlled trials (RCTs) reporting on the efficacy or safety of relapsed or refractory CLL and if outcomes for CLL were reported separately from trials that included other lymphoid neoplasms. We used the Bucher method for conducting adjusted indirect comparisons within a meta-analysis. We identified 6 RCTs of pharmacologic treatment for relapsed/refractory CLL. The most common drugs investigated (alone or in combination) were fludarabine and cyclophosphamide. When reported, median overall survival ranged from 27.3 to 52.9 months, and overall response rate from 58% to 82%. Although meta-analysis of efficacy results was considered, details are not presented because only 3 studies qualified and the common comparator treatment was not clinically relevant. The relatively small number of RCTs, few overlapping treatment arms, and variability in end points studied make it difficult to formally compare therapies for relapsed/refractory CLL. Significant variability in RCT features presents a further challenge to meaningful comparisons. Additional well-designed RCTs are needed to fully understand the relative efficacy and safety of older and more recently developed therapies.