On the Application of Flexible Designs When Searching for the Better of Two Anticancer Treatments

In search for better treatment, biomedical researchers have defined an increasing number of new anticancer compounds attacking the tumour disease with drugs targeted to specific molecular structure and acting very differently from standard cytotoxic drugs. This has put high pressure on early clinical drug testing since drugs may need to be tested in parallel when only a limited number of patients—e.g., in rare diseases—or limited funding for a single compound is available. Furthermore, at planning stage, basic information to define an adequate design may be rudimentary. Therefore, flexibility in design and conduct of clinical studies has become one of the methodological challenges in the search for better anticancer treatments. Using the example of a comparative phase II study in patients with rare non-clear cell renal cell carcinoma and high uncertainty about effective treatment options, three flexible design options are explored for two-stage two-armed survival trials. Whereas the two considered classical group sequential approaches integrate early stopping for futility in two-sided hypothesis tests, the presented adaptive group sequential design enlarges these methods by sample size recalculation after the interim analysis if the study has not been stopped for futility. Simulation studies compare the characteristics of the different design approaches.