Introduction: Women continue to be underrepresented in oncology clinical trials, leading to poor, underpowered subgroup analyses that cannot be generalized to cancer patients in practice. In 2014, the US Food and Drug Administration (FDA) released an Action Plan, which included actions to improve the quality and reporting of demographic subgroup data. We sought to evaluate the five-year progress since the release of this report by assessing the credibility of sex-specific subgroup analyses in oncology clinical trials.