To examine the response rate of gross chemo-refractory breast cancer treated with concurrent capecitabine (CAP) and radiation therapy in a prospective Phase II study.

Breast cancer patients with inoperable disease after chemotherapy, residual nodal disease after definitive surgical resection, unresectable chest wall or nodal recurrence after a prior mastectomy, or oligometastatic disease were eligible. Response by RECIST criteria was assessed after 45 Gy. Conversion to operable, locoregional control, and grade ≥3 toxicities were assessed. The first 9 patients received CAP 825 mg/m twice daily continuously. Because of toxicity, subsequent patients received CAP only on radiation days. Kaplan-Meier analysis was used to estimate overall survival (OS) and locoregional recurrence-free survival.

From 2009 to 2012, 32 patients were accrued; 26 received protocol-specified treatment. Median follow-up was 12.9 months (interquartile range, 7.10-42.9 months). Nineteen patients (73%) had partial or complete response. Fourteen patients (53.9%) experienced grade 3 non-dermatitis toxicity (7 of 9 continuous dosing). Three of four inoperable patients converted to operable. One-year actuarial OS in the treated cohort was 54%. The trial was stopped early after interim analysis suggested futility independent of response. Treatment was deemed futile (ie, conversion to operable but M1 disease immediately postoperatively) in 9 of 10 patients with triple-negative (TN) versus 6 of 16 with non-TN disease (P=.014). Median OS and 1-year locoregional recurrence-free survival among non-TN versus TN patients was 22.8 versus 5.1 months, and 63% versus 20% (P=.007).

Capecitabine can be safely administered on radiation days with careful clinical monitoring and was associated with encouraging response in this chemo-refractory cohort. However, patients with TN breast cancer had poor outcomes even when response was achieved. Further study in non-TN patients may be warranted.