Twenty-year Experience in the Management of Anal Carcinoma with Interstitial Brachytherapy

Abstract

The management of anal cancer has undergone an interesting transformation over the last three decades. The idea of organ preservation emerged following the discovery of a high complete response rate from preoperative combined chemoradiation prior to abdominal-perineal resection. Radiotherapy, with concomitant chemotherapy for advanced tumors, is now the standard first-line treatment for anal carcinoma. The combination of external beam radiotherapy with interstitial brachytherapy increases the dose to the tumor volume and limits the volume of irradiated normal tissue, thereby decreasing late toxicity. We present an analysis of a series of patients treated with iridium 192 low-dose rate (LDR) or pulsed-dose rate (PDR) interstitial brachytherapy for anal carcinoma. From 1989 to 2009, 38 patients with anal carcinoma were treated with brachytherapy at the Catalan Institute of Oncology in Spain, in 26 cases with LDR and in 12 cases with PDR. The median age was 62 years (range, 38-86), with a male/female gender ratio of 20/18. The TNM classification was as follows: 10 T1, 22 T2, 5 T3, and 1 T4; 32 N0, 3 N1, and 3 N2. Treatment started with concomitant chemoradiotherapy in 22 patients or radiotherapy alone in 10 patients. The mean dose of external beam irradiation given to the posterior pelvis was 45 Gy (range, 32-50 Gy). The median dose for interstitial brachytherapy was 20 Gy (range, 15-35) for the boost and 60-65 Gy if monotherapy. Of the 38 patients, 34 (89.4%) were recorded as complete response, 2 (5.3%) as partial response and 2 (5.3%) as progression disease. The procedure was well tolerated. With a median follow-up of 30 months (range, 3.7-200.7), 2 and 5-year overall survival was 87% (95% CI: 74-98%) and 76% (95% CI: 59-93%), respectively. The 2, 5, and 10-year local progression-free survival rate was 91% (95% CI: 81-100%), 87% (95% CI: 75-99%), and 81% (95% CI: 67-97%), respectively. Twelve relapses occurred (3 regional and distant, 3 distant alone, 1 regional alone, and 5 local). Two patients had chronic mucositis grade III/IV (Radiation Therapy Oncology Group scale). No colostomy was required for necrosis. Two patients experienced serious late toxicity grade 3/4 mucositis and only three patients (7.8%) had incontinence after brachytherapy. No correlation was found between the dose rate and late mucositis (p = 1) or dermatitis (p = 0.4). LDR and PDR appear to be an effective treatment for anal carcinoma with good local tumor control at 10 years, low rates of late toxicity and preservation of the anal sphincter. Evaluating an optimized interstitial brachytherapy technique aimed at reducing toxicity to normal tissues and/or increasing the dose to the tumor volume remains to be done.