Purpose: To investigate the incidence, time course, and relation to irradiated volumes of late morbidity after three-dimensional conformal radiation therapy (RT) for prostate cancer.
Methods and materials: From January 2000 to December 2001, a total of 247 patients with prostate cancer received a target dose of 70 Gy using conformal RT. Forty-eight patients (20%) received irradiation to the prostate only (Group P), 154 patients (62%) received irradiation to the prostate and seminal vesicles (Group PSV), and 45 patients (18%) received modified pelvic fields (Group MPF). Androgen deprivation was given to 86% of patients. Median follow-up was 62 months. Late gastrointestinal (GI) and genitourinary (GU) morbidity were recorded according to the Radiation Therapy Oncology Group scoring system.
Results: We observed 9%, 7%, and 25% Grade 2 or higher GI morbidity and 36%, 30%, and 21% Grade 2 or higher GU morbidity in Groups P, PSV, and MPF, respectively. In multivariate analyses, age and treatment group were independent predictors for the incidence of late Grade 2 or higher GI morbidity, whereas age and urinary symptoms before treatment were independent predictors for late Grade 2 or higher GU morbidity. Acute side effects predicted for late effects. The rectum dose-volume histogram parameters correlated with the incidence of late Grade 2 or higher GI morbidity, especially the fractional volume receiving more than 40-43 Gy. At 5 years of follow-up, the rate of Grade 2 late GI morbidity was only 1.4%, and Grade 2 or higher GU morbidity was 10.6%.
Conclusions: The data presented here show that late GI morbidity after prostate RT is low and subsides with time.