Short-term Toxicity of High Dose Rate Brachytherapy in Prostate Cancer Patients with Inflammatory Bowel Disease

Aims: Inflammatory bowel disease (IBD) has historically been considered a risk factor for increased bowel toxicity in patients receiving pelvic external beam radiotherapy. The risk is reduced in intensity-modulated radiotherapy compared with three-dimensional conformal radiotherapy. The effect of brachytherapy has been less extensively researched. Despite the increased dose to the gross tumour volume and decreased dose to organs at risk, previous studies have recommended avoidance of low dose rate (LDR) brachytherapy in patients with IBD, due to increased bowel toxicity. We investigated the effect of high dose rate (HDR) brachytherapy in IBD. Materials and methods: Eleven IBD patients across four different sites (in the UK and Spain) who received HDR brachytherapy, between 2012 and 2015, were followed for up to 12 months. Acute bowel and urinary toxicity data were collected and recorded. Results: The median length of follow-up was 6 months (range between 6 weeks and 12 months). Five patients had Crohn's disease and six patients had ulcerative colitis. Only one patient (with Crohn's disease) had active disease at the time of treatment. This patient reported no bowel toxicity. Of the remaining patients, two suffered grade 1 diarrhoea (at 6 weeks and 6 months); three suffered grade 1 proctitis (at 6 weeks and 6 months). There was no grade ≥2 bowel toxicity. The most severe toxicity was grade 2 urinary frequency in one patient (at 6 weeks). Discussion: This small, prospective case series suggests that, in the short term, HDR brachytherapy is safe and well tolerated in IBD patients. Therefore, IBD should not automatically disqualify patients from, at least, HDR brachytherapy. The reason why these results differ from previous LDR studies possibly reflects the benefit of inverse planning, which more readily achieves rectal dose constraints in HDR brachytherapy