Acute morbidity related to treatment volume during 3D-conformal radiation therapy for prostate cancer

Abstract

Purpose To investigate the relation between acute toxicity and irradiated volume in the organs at risk during three-dimensional conformal radiation therapy for prostate cancer. Methods and materials From January to December 2001, we treated 132 prostate cancer patients to a prescribed target dose of 70 Gy. Twenty-six patients (20%) received irradiation to the prostate only (Group P), 86 patients (65%) had field arrangements encompassing the prostate and seminal vesicles (Group PSV) while 20 (15%) received modified pelvic fields (Group MPF). A four-field conformal box technique was used. Acute toxicity according to the RTOG scoring system was prospectively recorded throughout the course of treatment. Results Overall, radiation was well tolerated with 11%, 16% and 35% Grade 2 gastro-intestinal (GI) toxicity and 19%, 34% and 35% Grade 2 or higher genito-urinary (GU) toxicity in Groups P, PSV and MPF, respectively. In univariate and multivariate analyses treatment group was a significant predictor for Grade 2 or higher acute morbidity. In multivariate logistic regression, the rectum dose–volume histogram parameters were correlated to the incidence of acute Grade 2 GI toxicity, with the fractional volumes receiving more than 37–40 Gy and above 70 Gy showing the statistically strongest correlation. The fractional bladder volume receiving more than 14–27 Gy showed the statistically strongest correlation with acute GU toxicity. Conclusions 3D-CRT radiation therapy to 70 Gy for prostate cancer was well tolerated. Only two of the 132 patients in the cohort experienced acute bladder toxicity Grade 3, none had Grade 3 rectal toxicity. Uni- and multivariate analyses indicated that the volume treated was a significant factor for the incidence of Grade 2 or higher acute morbidity.