Interstitial brachytherapy as a boost to patients with anal carcinoma and poor response to chemoradiation: Single-institution long-term results.

PURPOSE: To analyze the efficacy of a protocol-based brachytherapy (BT) boost after external beam radiation therapy (EBRT) with simultaneous chemotherapy in patients with anal carcinoma.

METHODS AND MATERIALS: About 190 patients have been analyzed. Around 143 patients were identified with a good clinical response at the end of EBRT. Another 47 patients received an additional BT boost to the residual tumor at 6 weeks after end of chemoradiation.

RESULTS: The 5-year incidence of local recurrence was 24% in patients with BT boost and 19% in patients without BT boost (p = 0.238). The 5-year disease-free survival rate, overall survival rate, and colostomy-free survival rate were 64% and 75% and 76.1% in the BT group and 69% (p = 0.212), 72% (p = 0.924), and 82.7% (p = 0.488) in the non-BT group. We found no differences in late toxicity between the groups.

CONCLUSIONS: For patients with anal cancer with not a good response to 50-59 Gy EBRT with simultaneous chemotherapy, the further dose escalation using the BT boost up to a mean of 67.5 Gy seems to improve the clinical outcome to the same level as observed in patients with a good response to ERBT, without an increase in late side effects.