Adaptive seamless design for an efficacy trial of replication-competent adenovirus-mediated suicide gene therapy and radiation in newly-diagnosed prostate cancer (ReCAP Trial)

PurposeCumulative evidence has suggested investigation of the efficacy of Replication-Competent Adenovirus-mediated Suicide Gene Therapy in newly-diagnosed Prostate Cancer (ReCAP). There is a challenge in designing an efficacy trial for newly-diagnosed prostate cancer given its long natural history. The regulatory agency recommended a Phase II trial for safety before conducting the efficacy trial.Experimental designThe ReCAP trial is an adaptive seamless, multi-site open-label, randomized Phase II/III trial. Two hundred eighty men will be randomized to receive either replication-competent adenovirus-mediated suicide gene therapy followed by radiation (Arm 1) or radiation alone (Arm 2). Phase II trial component will include the first 21 patients in Arm 1 with complete toxicity through day 90 for safety evaluation. The primary efficacy endpoint is the time free from biochemical and/or clinical failure (FFF). The secondary efficacy endpoints are 2-year prostate biopsies and overall survival. Unequal spaced interim looks are proposed with the adaptive sample-size re-estimation.ResultsThis trial has been approved by the FDA for the study therapy investigation and is currently recruiting patients.ConclusionsChallenges remain in designing newly-diagnosed prostate cancer trials. Adaptive seamless design is time-saving and a cost-effective design in the development of novel medical therapies, but requires a specified statistical plan in the decision process involved.