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Proctitis after conventional external radiation therapy for prostate cancer: importance of minimizing posterior
1Department of Therapeutic Radiology-Radiation Oncology, University of Minnesota Hospital and Clinics, Minneapolis 55455, USA.
Purpose:
To identify factors associated with the prevalence of radiation proctitis in patients with prostate cancer treated with external radiation therapy and to determine if a dose-response relationship exists.
Materials And Methods:
The study included 101 prostate cancer patients treated at the University of Minnesota Hospital and Clinics between 1970 and 1987. Radiation therapy at a daily dose of 175-200 cGy was given for 5 consecutive days per week for 7 weeks with a 10-24-MV linear accelerator. Mean dose to the prostate was 6,795 cGy (range, 5,579-7,417 cGy). Simulation radiographs obtained with rectal barium were analyzed in 51 patients. Doses were calculated at specific points in the boost field.
Results:
Radiation proctitis developed in 19 patients. No pretreatment or treatment factors were associated with a higher prevalence of proctitis. Statistically significant correlation (P < .042) was found between the development of proctitis and dose to the posterior rectum. At chi 2 analysis, proctitis was statistically significantly (P < .005) associated with posterior rectal doses of > 5,000 cGy.
Conclusion:
A high posterior rectal dose (> 5,000 cGy) is associated with increased prevalence of proctitis after radiation therapy.