Robotic-Based SBRT for Prostate Cancer is Well Tolerated in Patients with a History of Inflammatory Bowel Disease

Abstract

Inflammatory bowel disease (IBD) is considered a relative contraindication to radiation therapy directed to the pelvis. Previous publications have demonstrated safety of carefully delivered image guided radiation therapy (IGRT) and brachytherapy in patients with inactive disease. Stereotactic Body Radiation Therapy (SBRT) is an increasingly utilized treatment option for men with localized prostate cancer, which utilizes smaller target volumes. This study reports our initial experience in men with inactive IBD who were treated with definitive robotic-based SBRT for prostate malignancy. We conducted a retrospective query of 3295 patients in our institutional review board approved database for patients with prostate cancer who had a comorbidity of IBD and were treated with SBRT. We cross-referenced follow-up visits, EPIC-questionnaires, and dosimetry tables to assess treatment related toxicity. Between December 10, 2010 and August 11, 2017, 19 patients with IBD and prostate cancer were treated with definitive robotic-based SBRT. 12 (63.2%) were diagnosed with Ulcerative Colitis and 7 (36.8%) with Crohn’s disease. Long-term rectal toxicity was characterized as occurring ≥6 months post radiation and scored by RTOG late toxicity scale. Of the 19 patients identified, 13 patients took nonsteroidal anti-inflammatory medications for their IBD; 1 took prednisone, and 2 patients received anti-coagulation medications for unrelated comorbidities prior to treatment. For this cohort, the median pre-treatment PSA was 7.3ng/ml (3-49.1ng/ml). Based on NCCN risk categories, 31.6%, 47.4% and 21.1% had low, intermediate, and high-risk disease, respectively. 5 patients were treated with concurrent Androgen Deprivation Therapy (ADT). The median prescription dose received was 3500cGy (3500-3625) delivered in 5 fractions. Patients received intrarectal amifostine prior to each fraction. The median age was 68 years (52-84). The mean Rectal maximum point dose was 3816.7cGy (3707.2-3997.1) and the mean rectal V3600cGy was 0.9cc’s (0.1-4.0). 5 patients have follow-up greater than 12 months and the median follow-up is 6 months (1-38). Thus far, treatment has been well tolerated by this cohort. 1 patient (5.3%) experienced ≥ grade 2 toxicity, with rectal fullness 12 months post-treatment; symptoms fully responded to proctofoam, with no further episodes on subsequent encounter. No cases of grade 3 toxicity, non-hemorrhoidal bleeding, or IBD flare have been reported. With a small sample size and modest follow-up, SBRT for selected patients with IBD who have prostate cancer appears well tolerated, with long-term follow-up continuing to evolve. Judicious use of tight posterior margins and intrarectal amifostine might confer a benefit regarding acute and chronic rectal toxicity. Caution should remain employed treating this patient cohort with larger fraction sizes even in high volume clinics.