Beyond clinical trials: CDK4/6 inhibitor efficacy predictors and nomogram model from real‐world evidence in metastatic breast cancer

Abstract

BackgroundCDK4/6 inhibitors (CDK4/6i) have shown promising results in the treatment of hormone receptor‐positive (HR+) metastatic breast cancer (MBC) when combined with endocrine therapy (ET). It is crucial to evaluate the actual effectiveness and safety of CDK4/6i in clinical practice, as well as to analyze the factors that can predict their outcomes.MethodsPatients with HR+ MBC who received CDK4/6i‐based therapy between May 2016 and May 2023 at Hunan Cancer Hospital were evaluated for progression‐free survival (PFS). Adverse reactions were assessed based on the National Cancer Institute Common Toxicity Criteria (version 5.0).ResultsThis study included 344 patients, with a median PFS (mPFS) of 12.8 months (range: 10.4–15.2 months). After adjustment, Cox multivariate regression analysis revealed that visceral metastasis (specifically liver and brain metastases), Eastern Cooperative Oncology Group Performance Status (ECOG PS) ≥ 1, estrogen receptor ≤ 80%, progesterone receptor ≤ 10%, Ki‐67 > 30%, and treatment in later stages were significant factors associated with reduced PFS. Based on this, we created a prognostic nomogram and validated its performance, obtaining a C‐index of 0.714 (95% confidence interval: 0.640–0.787) as well as reliable calibration and clinical impact. The mPFS of CDK4/6i rechallenge was 7.7 months; for patients who initially discontinued CDK4/6i for reasons other than disease progression, CDK4/6i rechallenge still provided a mPFS of 11.4 months. The tolerability and safety of combining CDK4/6is with ET were manageable. Adverse events led to treatment discontinuation in 3.8% of patients. Neutropenia (29.1%), leukopenia (13.7%), and anemia (4.1%) were the primary grade 3/4 adverse reactions.ConclusionsThis real‐world study highlights the ample efficacy and reasonable safety of combined CDK4/6i and ET in patients with HR+ MBC. Individualized treatment decisions and ongoing safety monitoring are important to optimize the therapeutic benefit of CDK4/6i treatment.