Safety profile of cyclin-dependent kinase (CDK) 4/6 inhibitors with concurrent radiation therapy: A systematic review and meta-analysis

•Available evidence derived from small heterogenous retrospective series.•Reliable reporting on RT doses, schedules, techniques, and intent is missing.•Overall results are in line with main phase 3 trials testing CDK4/6i in advanced breast cancer.•No data on concurrent CDK4/6i and RT exist in the early breast cancer phase 3 trials.•While further research on treatments combination is needed, international consensus recommendations is awaited.