Overall Survival of CDK4/6-Inhibitor-Based Treatments in Clinically Relevant Subgroups of Metastatic Breast Cancer: Systematic Review and Meta-Analysis.

BACKGROUND: Cyclin-dependent kinases 4 and 6 (CDK4/6) inhibitors + endocrine therapy (ET) prolonged progression-free survival as first- or second-line therapy for hormone receptor-positive (HR+)/HER2-negative metastatic breast cancer prognosis. Given the recent publication of overall survival (OS) data for the 3 CDK4/6-inhibitors, we performed a meta-analysis to identify a more precise and reliable benefit from such treatments in specific clinical subgroups. METHODS: We conducted a systematic literature search to select all available phase II or III randomized clinical trials of CDK4/6-inhibitors + ET reporting OS data in first- or second-line therapy of HR+/HER2-negative pre- or postmenopausal metastatic breast cancer. A random effect model was applied for the analyses. Heterogeneity was assessed with I2statistic. Subgroup analysis was performed to explore the effect of study-level factors. The project was registered in the Open Science Framework database (doi: 10.17605/OSF.IO/TNZQP). RESULTS: Six studies were included in our analyses (3421 patients). A clear OS benefit was observed in patients without (hazard ratio [HR] = 0.68, 95% confidence interval [CI] = 0.54 to 0.85, I2 = 0.0%) and with visceral involvement (HR = 0.76, 95% CI = 0.65 to 0.89, I2 = 0.0%), with at least 3 metastatic sites (HR = 0.75, 95% CI = 0.60 to 0.94, I2 = 11.6%), in an endocrine-resistant (HR = 0.79, 95% CI = 0.67 to 0.93, I2 = 0.0%) and sensitive subset (HR = 0.73, 95% CI = 0.61 to 0.88, I2 = 0.0%), for younger than 65 years (HR = 0.80, 95% CI = 0.67 to 0.95, I2 = 0.0%) and 65 years or older (HR = 0.71, 95% CI = 0.53 to 0.95, I2 = 44.4%), in postmenopausal (HR = 0.76, 95% CI = 0.67 to 0.86, I2 = 0.0%) and pre- or perimenopausal setting (HR = 0.76, 95% CI = 0.60 to 0.96, I2 = 0.0%) as well as in chemotherapy-naïve patients (HR = 0.72, 95% CI = 0.55 to 0.93, I2 = 0.0%). CONCLUSIONS: CDK4/6-inhibitors + ET combinations compared with ET alone improve OS independent of age, menopausal status, endocrine sensitiveness, and visceral involvement and should be preferred as upfront therapy instead of endocrine monotherapy.

Gene expression profiling in breast cancer: a clinical perspective.

Gene expression profiling tests are used in an attempt to determine the right treatment for the right person with early-stage breast cancer that may have spread to nearby lymph nodes but not to distant parts of the body. These new diagnostic approaches are designed to spare people who do not need additional treatment (adjuvant therapy) the side effects of unnecessary treatment, and allow people who may benefit from adjuvant therapy to receive it. In the present review we discuss in detail the major diagnostic tests available such as MammaPrint dx, Oncotype dx, PAM50, Mammostrat, IHC4, MapQuant DX, Theros-Breast Cancer Gene Expression Ratio Assay, and their potential clinical applications.