Toxicity and survival of anal cancer patients treated with intensity-modulated radiation therapy

Abstract

Introduction: The definitive treatment of anal cancer with chemoradiotherapy spares abdominoperineal resection for salvage treatment but carries a high burden of toxicity. Intensity-modulated radiation therapy has been implemented to reduce toxicity, reduce treatment breaks and improve survival. However, large and long-term studies are lacking. We aimed to investigate the toxicities and long-term survival of anal cancer patients treated with intensity-modulated radiation therapy at James Cook University Hospital, Middlesbrough.

Materials and methods: We conducted a retrospective analysis of all patients with squamous cell anal cancer treated at James Cook University Hospital between July 2010 and April 2017. All patients were uniformly treated with intensity-modulated radiation therapy-based chemoradiation with curative intent. A subset of these patients was followed-up prospectively by an oncologist for acute and late toxicity. We calculated Kaplan-Meier estimates of survival statistics and compared our results with those of previous trials which used conventional radiotherapy.

Results: We studied 132 patients, including a toxicity subset of 64, for a median follow-up time of 43 months (range 3-84 months). Eleven patients (8.3%) underwent salvage abdominoperineal resection. Grade 3+ acute non-haematological, gastrointestinal, genitourinary and dermatological toxicity were found in 56.2%, 12.3%, 0% and 50.7% of the toxicity subset (n = 64). Median treatment duration was 37 days. Overall and colostomy-free survival at five years were 68.3% and 85.3%, respectively. Tumour size (P = 0.006) and age (P = 0.002) predicted shorter overall survival.

Conclusions: Intensity-modulated radiation therapy probably reduces acute gastrointestinal and genitourinary toxicity compared with conventional radiotherapy, while resulting in similar overall and colostomy-free survival. We suggest that further dose escalation may improve survival in patients with T3/T4 tumours.

Keywords: Abdominoperineal resection; Anal cancer; Chemoradiation; Intensity-modulated radiation therapy; Survival; Toxicity.

Figure 1

Survival curves representing the Kaplan-Meier estimates of survival: a) overall; b) colostomy-free; c) disease-free.

Figure 2

Survival curve representing the Kaplan–Meier estimate of metastasis-free survival. The y axis represents the fraction of those patients who would eventually be found to have a distant metastasis (n = 19) who are metastasis-free. The x axis represents the time from initiation of treatment in months. The non-parametric survival curve is calculated using interval-censored data.

Figure 3

Comparison of overall survival for patients who received 50.4 Gy compared with those who received 54 Gy to the main tumour volume.

Figure 4

Comparison of overall survival for T1, T2, T3 and T4 tumours represented by Kaplan–Meier curves.