直腸癌術後患者の前立腺癌に対する IMRT の成績
演題番号 : O5-3
Prostate cancer patients who have undergone surgery for rectal cancer are rare; therefore, no consensus has been established about radiation dose constraints for rectal anastomosis. In our protocol we reduced the total prescribed dose from 78 Gy to 74 Gy , and the dose to the rectal anastomosis was limited up to 70 Gy using intensity-modulated radiotherapy (IMRT). This retrospective study aimed to evaluate the toxicity and dose-volume data of patients treated according to the protocol.
Materials and Methods
Prostate cancer patients who were treated definitively with IMRT between January 2000 and December 2019 and who had undergone rectal surgery before the IMRT were identified from our database. Only patients whose rectal anastomoses were observed within 10 mm around the planning target volume were included. Acute and late toxicities were analyzed according to the Common Terminology Criteria for Adverse Events ver. 5.0. Biochemical recurrence-free survival (BRFS), prostate cancer-specific survival (PCSS), and overall survival (OS) were estimated using the Kaplan-Meier method.
Fourteen patients were analyzed. The median patient age was 71 years, and the median follow-up period was 65 months (range: 12-110). The median total dose was 74 Gy (range: 70-78). The median maximum dose to the rectal anastomosis was 65.7 Gy (IQR: 53.2-68.8). The incidence rates of grade 2 acute urinary (GU) and rectal toxicities (GI) were 14.3% and 0%, respectively, and no grade ≥3 toxicities were observed. Neither grade ≥2 GU nor GI late toxicities were observed. The 5-year BRFS, PCSS, and OS were 92.3%, 100%, and 100%, respectively.
Among prostate cancer patients who had undergone rectal surgery, IMRT achieved the long-term safety of rectal anastomosis without compromising oncologic outcomes, when maximum doses to the anastomosis were limited up to 70 Gy.