Difference in the rate of rectal complications following prostate brachytherapy based on the prostate-rectum distance and the prostate longitudinal length among early prostate cancer patients

PURPOSE To investigate the difference in rectal complications rate following prostate low dose rate (LDR) brachytherapy based on prostate-rectum distance and prostate longitudinal length among early prostate cancer patients. MATERIALS AND METHODS From March 2008 to February 2013, 245 prostate cancer patients with a Gleason score ≤7 were treated with 125-I LDR brachytherapy. Among them, 178 patients with prostate volume 20-35 mL and a follow-up period ≥6 months were evaluated for radiation proctitis. Magnetic resonance imaging (MRI) was performed for a prebrachytherapy evaluation, and prostate-rectum distance and prostate longitudinal length were measured. The radiation proctitis was confirmed and graded via colonoscopy based on the radiation therapy oncology group (RTOG) toxicity criteria. RESULTS Twenty-three patients received a colonoscopy for proctitis evaluation, and 12 were identified as grade 1 on the RTOG scale. Nine patients were diagnosed as grade 2 and 2 patients were grade 3. No patient developed grade 4 proctitis. The rectal-complication group had a mean prostate-rectum distance of 2.51±0.16 mm, while non-rectal-complication control group had 3.32±0.31 mm. The grade 1 proctitis patients had a mean prostate-rectum distance of 2.80±0.15 mm, which was significantly longer than 2.12±0.31 mm of grades 2 and 3 patient groups (p=0.045). All 11 patients of grades 2 and 3 had a prostate longitudinal length of 35.22±2.50 mm, which was longer than group 1, but the difference was not statistically significant (p=0.214). CONCLUSIONS As the prostate-rectum distance increased, fewer postimplantation rectal symptoms were observed. Patients with a shorter prostate-rectum distance in MRI should receive modified implantation techniques or radical prostatectomy.