High dose rate brachytherapy in the management of anal cancer: A review

Abstract

Purpose: To conduct a systematic review evaluating the impact of high dose rate (HDR) brachytherapy (BT) on the clinical outcomes and toxicities of patients with anal cancer.

Methods and materials: A search of Medline, Embase, and Cochrane Library databases was performed using search terms: "anal", "anal canal", "squamous", "adenocarcinoma", "cancer", "neoplasm", in combination with "brachytherapy", "high dose rate brachytherapy" or "HDR brachytherapy". Additional studies were identified after scanning references. Studies published in English with ≥10 patients were included.

Results: Ten studies (n = 448) were included in this review. 321 patients were treated with curative intent external beam radiotherapy (EBRT), chemotherapy (CT) and HDRBT; of those, 312 and 9 received interstitial and intraluminal BT, respectively. Mean follow up was 39.9 months (range (R): 24-61 months). Complete response was noted between 80%-93% and local control ranged between 81%-88%. Mean rate of local failure was 12.3% (SD 3.6%, R: 8%-18%). Distant failure rate was reported between 2%-3% and metastasis free survival ranged between 82%-88%. Mean disease free survival and overall survival were 77.3% (SD 6.6%, R: 66%-100%) and 82.5% (SD 13.7%, R: 70%-87.7%). Acute toxicity was mostly grade 1/2 dermatitis, proctitis or cystitis; G3 or higher toxicity was reported only in 4 patients in 2 studies (dermatitis n = 3 and sphincter necrosis n = 1). Most common long term toxicities were incontinence (2.5%-9%) and proctitis (2.5%-19%); G3/4 toxicity ranged between 2.2%-7.1%. Mean sphincter preservation rate and colostomy free survival was 88.0% and 80.4%, respectively.

Conclusion: Pooled analysis in this review suggests excellent response, local control and survival with HDRBT in combination with EBRT and CT, with limited toxicity. Prospective well conducted trials are needed to further establish role of HDRBT management of anal cancer with future focus on development of international consensus on patient selection, dosimetric parameters, treatment sequencing as well as defining uniform outcome and toxicity assessment.

Keywords: Anal cancer; Brachytherapy; High dose rate; Review.