Toxicity of the lower gastrointestinal tract and its predictive factors after 72Gy conventionally fractionated 3D conformal radiotherapy of localized prostate cancer.

PURPOSE To estimate the incidence of acute and late lower gastrointestinal tract toxicity (LGIT) in patients treated with 3D conformal radiotherapy (3DCRT) for localized prostate cancer (PC) and estimate the influence of dosimetric parameters and other possible factors. METHODS Ninety-four patients with localized PC treated with 3DCRT, with an estimated risk of lymph node involvement ?15%, according to the Roach formula, were evaluated in this study. All patients received a total dose of 72Gy in 36 fractions. Acute and late lower gastrointestinal tract (LGIT) toxicity were graded according to the EORTC radiation morbidity scoring scale. Characteristics such as alcohol intake, gastrointestinal (GI) co-morbidities, hemorrhoids, previous abdominal or pelvic surgery (PAPS), diabetes mellitus (DM), the use of antiaggregants, and dosimetric parameters, were analyzed as possible predictive factors of radiation (RT) toxicity. RESULTS Grade ?1 acute LGIT toxicity during 3DCRT developed in 41 of 94 patients (43.6%). At univariate logistic regression analysis (UVA) using the baseline model, alcohol consumption (p=0.068), hemorrhoids (p=0.004), GI co-morbidities (p=0.018), PAPS (p=0.033), V60 (p=0.070), V65 (p=0.046) and V70 (P=0.056) were significant predictive factors for any grade of acute LGIT toxicity. Predictive factors of grade ?1 acute toxicity in the multivariate logistic regression analysis (MVA) were current hemorrhoids (p=0.007), and the GI co-morbidities (p=0.025). Late grade 1 LGIT toxicity occurred in 17 (18.1%) patients. Late grade ?2 LGIT toxicity as a maximum toxicity score occurred in 9 (9.57%) patients during a median follow-up of 27 months. Following UVA, hemorrhoids (p=0.001) and use of antiaggregants (p=0.034) were significant predictive factors for any grade of late LGIT toxicity. In the MVA, hemorrhoids were significantly associated with late grade ?1 LGIT toxicity (p=0.005). CONCLUSION Hemorrhoids and GI co-morbidities had a significant impact on the occurrence of acute grade ?1 LGIT toxicity. Hemorrhoids had significant influence on the development of any grade of late LGIT toxicity.