Outcome and Toxicity in the Modern Era of New Drugs for Multiple Myeloma: A Reappraisal for Comparison With Future Investigational Trials

The introduction of new drugs such as thalidomide, lenalidomide, and bortezomib has led to novel treatment strategies and significantly improved the outcome of patients with multiple myeloma (MM). The enhanced knowledge of myeloma pathogenesis has allowed the identification of new therapeutic targets and many clinical trials are either planned or in progress to evaluate these more selective drugs in the near future. The results of these studies, however, will have to be compared with the results of existing novel therapies for the treatment of MM in order to define whether new protocols do not duplicate current new standards and constitute a real improvement. We reviewed the results of a series of phase I, II, III studies with thalidomide, lenalidomide, and bortezomib combinations for newly diagnosed MM in order to define a reasonable standard in terms of activity, efficacy, and toxicity and to have a potentially useful starting point for comparisons with future investigational trials. Three-drug regimens appear to double the complete remission (CR) rate (20%), though regimens containing 4 drugs triple the CR rate (30%), compared with those containing only 2 agents (10%). These improvements in the depth and quality of response translate into a progressive increase in the progression-free survival rate at 2 years (from approximately 54%-62% to 75%, respectively). Conversely, by using additional agents, a marked increase in hematologic toxicity has been described (8%, 28%, and 28% respectively), whereas nonhematologic toxicity appears to be similar (26%, 24%, and 27%, respectively). These results suggest that new trials in the future will constitute significant progress if they can improve on the current relatively favorable efficacy/toxicity ratio. Nonetheless, exciting new combinations in development do hold promise and results from these studies are eagerly awaited.