Abstract
BACKGROUND: This study aimed to compare the efficacy of CDK4/6 inhibitors plus endocrine therapy in two groups of patients with HR-positive/HER2-negative metastatic breast cancer: those with symptomatic, high tumor burden disease and those with asymptomatic disease. DESIGN AND METHODS: This retrospective study included 193 patients who received either ribociclib or palbociclib in combination with first-line ET. Patients were divided into symptomatic and asymptomatic groups and compared regarding baseline characteristics and progression-free survivals (PFS). RESULTS: Symptomatic patients had a significantly shorter mPFS than asymptomatic patients (22.7 months vs. 35.0 months, p = 0.009). Among symptomatic patients, those treated with ribociclib had a longer mPFS than those treated with palbociclib (28.26 months vs. 17.18 months, p = 0.021). Multivariate analysis identified the symptomatic disease and liver metastasis as independent predictors of shorter mPFS (HR; 1.835, 95% CI; 1.146-2.939 and HR; 2.433, 95% CI; 1.329-4.454, respectively). CONCLUSION: Our analysis revealed that although symptomatic individuals who underwent CDK4/6 inhibitor plus ET experienced a significant reduction in mPFS durations compared to asymptomatic patients, the 22-month mPFS indicated that CDK4/6 inhibitor plus ET is an effective treatment option.