Capecitabine-Based Chemoendocrine Combination as First-Line Treatment for Metastatic Hormone-Positive Metastatic Breast Cancer: Phase 2 Study

Abstract

BackgroundPreclinical studies have suggested a synergistic effect of tamoxifen and capecitabine in estrogen receptor–positive cell lines. We evaluated the safety and efficacy of first-line chemoendocrine treatment in patients with metastatic breast cancer. Biochemical assessment was performed of serum levels of thymidine phosphorylase enzyme (TP), serum tamoxifen, hydroxytamoxifen, and 5-fluorouracil in relationship to efficacy. Patients and MethodsThis prospective phase 2 interventional study studied patients with estrogen receptor-positive, HER2− metastatic breast cancer who received either tamoxifen/capecitabine or letrozole/capecitabine as first-line treatment. The dose of capecitabine provided at 2000 mg per day continuously as a fixed dose. ResultsForty women with a median age of 49.3 years were enrolled. For the whole study group, median progression-free survival (PFS) was 10 months and median overall survival (OS) was 23.3 months. The overall response rate was 60% and the clinical benefit rate 82.5%. Progesterone receptor positivity was associated with significantly longer PFS (12 vs. 7 months, P = .021). The most frequent adverse events were palmar–plantar erythrodysesthesia (62.5%), fatigue (62.5%), diarrhea (30%), abdominal pain (12.5%), and constipation (10%). Changes in serum level of TP were not correlated to response to treatment, PFS, or OS. Higher serum levels of tamoxifen and hydroxytamoxifen were correlated with higher response rates and longer PFS but not OS. ConclusionChemoendocrine treatment is well tolerated, with no evidence of contradictory effects between the combination components. However, the efficacy data need more validation.