Clinical outcome after treatment with a brachytherapy boost versus external beam boost for anal carcinoma

PURPOSE: To evaluate the outcome after definitive whole pelvis external beam radiotherapy (EBRT) followed by brachytherapy (BT) boost after treatment break vs. external beam boost without break in the treatment of anal carcinoma. METHODS AND MATERIALS: Eighty-one consecutive patients with invasive anal carcinoma were analyzed retrospectively. Patients treated with an interstitial (192)Ir high-dose-rate (HDR) implant boost of 14Gy/7 fractions/3d given 3 weeks after completion of whole pelvis 45Gy EBRT were compared with those treated with external beam boost of 14.4Gy, started immediately after completion of whole pelvis 45Gy EBRT. Concomitant chemotherapy (CT) with mitomycin C was applied during whole pelvis EBRT depending on tumor stage. Pattern of care, local disease control (LC), cancer-specific survival (CSS), overall survival (OS), toxicity, and quality of life (QOL) were assessed. RESULTS: Radiotherapy with or without concomitant CT achieved clinical complete response in 93.4% of patients. In early stage tumors, (192)Ir-HDR BT boost with CT resulted in a 5-year LC and CSS of 100%. In all patients, BT boost did not result in improved LC, OS, and CSS compared with EBRT boost, despite stage and treatment bias favoring small tumors to be treated with BT. The 5-year and 10-year OS were 66% and 44% (BT boost) and 66% and 52% (EBRT boost), respectively. Subgroup analysis of Stages I and II disease revealed no significant improvement after BT boost compared with EBRT boost. Acute skin toxicity was less common in the BT boost group (whole cohort: p=0.14; Stages I-IIIa: p=0.05), but long-term morbidity and QOL were similar. No local necrosis was seen after BT boost and the 10-year sphincter preservation rate was 87% in these patients. CONCLUSIONS: Interstitial (192)Ir-HDR implant boost with break and EBRT boost without break yield similar results. Acute skin toxicity is reduced with BT boost but long-term morbidity and QOL are identical. BT boost is most beneficial in early stage tumors but the advantage of BT seems to be limited due to its invasiveness, doctor dependence, and logistic circumstances