Adult cancer clinical trials that fail to complete: an epidemic?

The number and diversity of cancer therapeutics in the pipeline has increased over the past decade due to an enhanced understanding of cancer biology and the identification of novel therapeutic targets. At the same time, the cost of bringing new drugs to market and the regulatory burdens associated with clinical drug development have progressively increased. The finite number of eligible patients and limited financial resources available to evaluate promising new therapeutics represent rate-limiting factors in the effort to translate preclinical discoveries into the next generation of standard therapeutic approaches. Optimal use of resources requires understanding and ultimately addressing inefficiencies in the cancer clinical trials system. Prior analyses have demonstrated that a large proportion of trials initiated by the National Cancer Institute (NCI) Cooperative Group system are never completed. While NCI Cooperative Group trials are important, they represent only a small proportion of all cancer clinical trials performed. Herein, we explore the problem of cancer clinical trials that fail to complete within the broader cancer clinical trials enterprise. Among 7776 phase II-III adult cancer clinical trials initiated between 2005-2011, we found a seven-year cumulative incidence of failure to complete of approximately 20% (95% confidence interval = 18% to 22%). Nearly 48000 patients were enrolled in trials that failed to complete. These trials likely contribute little to the scientific knowledge base, divert resources and patients from answering other critical questions, and represent a barrier to progress.