biostudies-literatureMai NNCI NIH HHS92https://www.ebi.ac.uk/biostudies/studies/S-EPMC11489574biostudies-literatureUnknown10(1)After disease progression on endocrine therapy (ET) plus a CDK4/6 inhibitor, there is no standardized sequence for subsequent treatment lines for estrogen receptor positive (ER+) metastatic breast cancer (MBC). CDK4/6i retrial as a treatment strategy is commonplace in modern clinical practice; however, the available prospective data investigating this strategy have had inconclusive results. To frame this data in a real-world context, we performed a retrospective analysis assessing the efficacy of CDK4/6is in 195 patients who had previous exposure to CDK4/6i in a prior treatment line at our institution. Among patients who had stopped a CDK4/6i due to toxicity, CDK4/6i retrial either immediately after with a different CDK4/6i or in a further treatment line with the same initial CDK4/6i was bNPJ breast cancerPredictors of response to CDK4/6i retrial after prior CDK4/6i failure in ER+ metastatic breast cancer.PMC11489574P30 CA008748Norton LRazavi PMai NModi SChandarlapaty SJhaveri KDos Anjos CHRobson MDrago JZDang CTPatil SSafonov AChen YLiu DBromberg JFfalsePredictors of response to CDK4/6i retrial after prior CDK4/6i failure in ER+ metastatic breast cancer.After disease progression on endocrine therapy (ET) plus a CDK4/6 inhibitor, there is no standardized sequence for subsequent treatment lines for estrogen receptor positive (ER+) metastatic breast cancer (MBC). CDK4/6i retrial as a treatment strategy is commonplace in modern clinical practice; however, the available prospective data investigating this strategy have had inconclusive results. To frame this data in a real-world context, we performed a retrospective analysis assessing the efficacy of CDK4/6is in 195 patients who had previous exposure to CDK4/6i in a prior treatment line at our institution. Among patients who had stopped a CDK4/6i due to toxicity, CDK4/6i retrial either immediately after with a different CDK4/6i or in a further treatment line with the same initial CDK4/6i was b2024-01-01T00:00:00Z2024 Oct2025-04-04T02:54:37.554Z2025-04-04T02:54:37.554ZS-EPMC114895743942463110.1038/s41523-024-00699-3