10680 Background: COX-2 is overexpressed during cancer progression in several solid tumors, including breast cancer, and constitutes an attractive therapeutic target. Selective COX-2 inhibitors, such as Celecoxib, have been successfully combined with fluoropyrimidine-based regimens, resulting in a lower-than-expected hematologic, GI, and skin toxicity rate. Methods: MBC pts who had progressed after at least one chemotherapy regimen for metastatic disease were eligible for the study. Capecitabine was administered at the starting dose of 1500–2000 mg/m2 daily for 14 days q3 wks. Celecoxib was administered at 200 mg b.i.d., continuously, starting on day 1. Dose escalation to Capecitabine 2000 or 2500 mg/m2 was allowed in the absence of toxicity > G1. Results: To date, 22 pts (median age: 55 yrs, range 35–81; ECOG PS 0: 21 pts) have been accrued; all pts had MBC and the majority had received adjuvant chemotherapy and hormonal treatment in the adjuvant and/or metastatic setting; all pts had been exposed to anthracyclines and/or taxanes. CapCel was administered as 2nd-, 3rd-, or ≥ 4th-line chemotherapy in 3, 10, and 9 pts, respectively. Capecitabine starting dose was 1500 mg/m2 in 9 pts and 2000 mg/m2 in 13 pts. Median number of cycles administered was 5 (range: 1–15). Toxicity was negligible: 1 pt experienced G3 neutropenia, 2 pts G3 skin/nail toxicity, and 1 pt G3 liver toxicity; all other toxicities were of grade ≤2. No Celecoxib-related GI or cardiovascular toxicities were observed. Capecitabine dose was escalated from 1500 to 2000 mg/m2 in 3/9 pts and from 2000 to 2500 mg/m2 in 2/13 pts, respectively, and reduced from 2000 to 1500 mg/m2 in 4/13 pts. Twenty pts are currently evaluable for response: 2 pts had PR (duration 48 and 49 wks, respectively), 15 pts had SD (median duration: 20 wks, range 12–44), and 3 pts progressed on therapy, for an overall clinical benefit rate of 40%. Median survival has not been reached. Conclusions: Overall, these preliminary results indicate that CapCel is extremely well-tolerated and has significant anti-tumor activity in a population of far advanced MBC pts. The study will continue to reach the projected accrual of 45 pts. No significant financial relationships to disclose.