Del Paggio JC, et al. - In this retrospective analysis, researchers sought to quantify the fragility index of phase 3, randomized, controlled trials supporting anticancer drugs that were approved by the US Food and Drug Administration (FDA) between January 1, 2014, and December 31, 2018. This analysis included only two-arm studies with 1:1 randomization and significant positive results for a time-to-event outcome. Of 36 identified studies, 17 (47%) were included in the fragility index analysis. The median fragility index was estimated to be 2 (IQR 0–27). In nine (53%) of 17 trials, 2 or less was the fragility index; the fragility index was 1% or less of the total sample size for these studies. Compared with the fragility index, the number lost to follow-up was higher in five (29%) of 17 trials. Overall, findings showed a low fragility index of many phase 3 randomized controlled trials supporting FDA-approved anticancer drugs, challenging confidence for concluding their superiority over control treatments. The robustness of clinical trial data might be evaluated via the fragility index, although it does not measure effect.