Prostate cancer radiotherapy (RT) in patients with (active) inflammatory bowel disease (IBD) remains controversial. We hypothesized that RT in combination with a biodegradable prostate-rectum spacer balloon implantation, might be a safe treatment approach with acceptable toxicities for these high risk for rectal toxicity patients.

We report on a small prospective mono-centric series of 8 patients with all-risk prostate cancer with the comorbidity of an IBD. Four patients had Crohn's disease and 4 patients had ulcerative colitis. One out of four had an active status of IBD. All patients were intended to be treated with curative high-dose RT: 5 patients were treated with external beam RT (70 Gray (Gy) in 28 fractions), and 3 patients were treated with I-implant (145 Gy). Toxicities were scored according to the CTCAE v4.03: acute side effects occur up to 3 months after RT, and late side effects start after 3 months.

Median follow-up was 13 months (range: 3-42 months). Only one acute grade 2 gastro-intestinal (GI) toxicity was observed: an increased diarrhea (4-6 above baseline) during RT, which resolved completely 6 weeks after treatment. No late grade 3 or more GI toxicity was reported, and no acute and late grade ≥2 genitourinary toxicity events were observed.

Prostate cancer patients with IBD are a challenge to treat with RT. Our results suggest that RT in combination with a balloon implant in selective patients with (active) IBD may be promising, however additional validation is needed.