Liang F, Wu Z, Mo M, et al. - Researchers examined differences in treatment effect size between randomized controlled phase 2 trials and subsequent phase 3 trials and investigated the potential predictor of positive phase 3 trials. Randomized controlled phase 2 studies published from January 2006 to December 2015 were identified from MEDLINE. They searched Web of Science, ClinicalTrials.gov and conference proceedings for matched phase 3 trials that investigated the same intervention in the same setting of same cancer. The search yielded 57 pairs of phase 2 and phase 3 trials. Phase 2 vs phase 3 trial exhibited 26% larger progression-free survival benefit. Overall 27% larger survival benefits were noted in phase 2 than phase 3 trial. Positive phase 2 trials were the only predictor of positive phase 3 trials.