Impact of celecoxib on capecitabine tolerability and activity in pretreated metastatic breast cancer: Results of a phase II study with biomarker evaluation

Background: Preclinical evidence suggests that the cyclo-oxygenase-2 (COX-2) enzyme plays an important role in breast cancer progression. The aim of the present phase II study was to determine the activity and safety of the combination of the COX-2 inhibitor celecoxib with capecitabine in metastatic breast cancer (MBC) patients pretreated with anthracyclines and/or taxanes. Methods: Eligible patients received capecitabine 1,000 mg/m2 twice daily on days 1-14 every 21 days and celecoxib 200 mg twice daily, continuously, until disease progression or unacceptable toxicity. Results: About 42 pretreated MBC patients were enrolled into the study. Median number of previous chemotherapy lines for metastatic disease was 2 (0-3). Seven patients (19%) responded to treatment while disease stabilization occurred in 17 patients (40.5%). Overall, 20 patients (47.5%) achieved clinical benefit [objective responses (CR) plus stable disease (SD) ≥6 months]. Median time to progression (TTP) and median overall survival (OS) were 5.2 and 17.8 months, respectively. Treatment was very well tolerated: grade 3 toxicities were observed in only five patients, respectively, and no grade 4 adverse events were reported. Celecoxib was never discontinued for toxicity. Analysis of COX-2 expression in the 22 patients with available tissue revealed a significantly longer TTP and OS for patients whose tumors over-expressed COX-2. Conclusions: The combination of capecitabine and celecoxib is active and safe in far advanced MBC patients. Interestingly, this association resulted in a lower-than-expected toxicity, as compared to single-agent capecitabine. The clinical relevance of COX-2 as determinant of sensitivity to treatment with celecoxib should be further evaluated in larger series of patients.