Single-Center Real World Study of Everolimus and Exemestane in HR+/HER2- Metastatic Breast Cancer Following CDK4/6 Inhibitor Therapy.

Background: Hormone receptor-positive (HR+), HER2- negative metastatic breast cancer (MBC) is the most common subtype of advanced breast cancer. Resistance to endocrine therapy often develops, particularly after CDK4/6 inhibitors. Everolimus, an mTOR inhibitor, may restore hormone sensitivity, but real-world data after CDK4/6 and chemotherapy are limited.

Methods: This retrospective, single-center study included 70 patients with HR+/HER2- MBC who progressed on CDK4/6 inhibitors and at least one line of chemotherapy. All received daily oral everolimus (10 mg) plus exemestane (25 mg). Tumor response was assessed via RECIST v1.1, and survival outcomes were estimated using the Kaplan-Meier method.

Results: Median progression-free survival was 6.6 months and overall survival was 22.6 months. The disease control rate was 88.6%, with 57.1% showing partial response. Fatigue (20%), skin toxicity (8.6%), and stomatitis (5.7%) were the most common adverse events. No grade 3-4 toxicities or discontinuations occurred. No clinical or pathological variables significantly influenced survival.

Conclusions: Everolimus plus exemestane provided meaningful clinical benefit and manageable toxicity in heavily pretreated HR+/HER2- MBC patients. This regimen remains a valid later-line option, particularly in settings with limited access to newer targeted therapies or genomic testing.