Intensity-modulated radiation therapy for prostate cancer after rectal surgery: a single hospital long-term safety analysis

Background: Radiotherapy is a treatment option for prostate cancer patients after rectal surgery; however, the toxicity profile of radiotherapy for such patients has not been elucidated. This study aimed to evaluate the long-term toxicities and efficacy of intensity-modulated radiotherapy (IMRT) in patients with prostate cancer who had undergone rectal surgery.

Methods: We retrospectively analyzed patients with prostate cancer after rectal surgery, who were definitively treated with IMRT between January 2000 and December 2019 at our institution. The planned total dose was 70-78 Gy in 2-Gy fraction, and the dose to the rectal anastomosis was limited to 70 Gy. The acute and late toxicities and survival outcomes were evaluated.

Results: Twenty patients were included in the analysis. The median age was 71 years, with a median follow-up of 86 months. The median time from surgery to IMRT was 93.5 months. The median prostate-specific antigen value was 13.17 ng/ml. The median total dose was 74 Gy, and the median maximum dose to rectal anastomosis was 66.97 Gy. The 8-year biochemical recurrence-free and overall survival rates were 70.2% and 90.0%, respectively. The incidence rates of grade 2 acute genitourinary and gastrointestinal toxicities were 14.3% and 0%, respectively. No grade ≥ 3 acute or late toxicities were observed when the rectal anastomosis dose was limited to 70 Gy.

Conclusions: This retrospective analysis suggested that IMRT for patients with prostate cancer after rectal surgery may be safe and effective with rectal dose constraint of D_max < 70 Gy if more than 5 years have passed after surgery.