Capecitabine Plus Aromatase Inhibitor as First Line Therapy for Hormone Receptor Positive, HER2 Negative Metastatic Breast Cancer

(1) Background: recent evidence suggests that long low-dose capecitabine regimens have a synergistic effect with endocrine therapy as aromatase inhibitors (AIs), and might increase overall survival for hormone-receptor-positive, HER2-negative, metastatic breast cancer compared to both treatments. We performed a retrospective study to confirm the efficacy and expand the safety data for capecitabine plus AI (a combination henceforth named XELIA) for this indication. (2) We conducted a single-center retrospective cohort study of 163 hormone receptor-positive metastatic breast cancer patients who received either the XELIA regimen, capecitabine, or an aromatase inhibitor (AI) as single agents in first-line treatment. The primary endpoint was progression-free survival, and the secondary endpoints were overall survival, best objective response, and toxicity incidence. (3) Results: the median progression-free survival for patients receiving XELIA, AI, and capecitabine was 29.37 months (20.91 to 37.84; 95% CI), 20.04 months (7.29 to 32.80; 95% CI) and 10.48 (8.69 to 12.28; 95% CI), respectively. The overall response rate was higher in the XELIA group (29.5%) than in the AI (14.3%) and capecitabine (9.1%) groups. However, the differences in overall survival were not statistically significant. Apart from hand-foot syndrome, there were no statistically significant differences in adverse events between the groups. (4) Conclusions: this retrospective study suggests that progression-free survival and overall response rates improved with the XELIA regimen compared to use of aromatase inhibitors and capecitabine alone. Combined use demonstrated an adequate safety profile and might represent an advantageous treatment in places where CDK 4/6 is not available. Larger studies and randomized clinical trials are required to confirm the effects shown in our study.