Gastro-intestinal and genito-urinary morbidity after 3D conformal radiotherapy of prostate cancer: observations of a randomized trial

Background and purpose: The late morbidity of a randomized study was analyzed after a follow up of 2 years. The difference in intestinal morbidity was analyzed as a function of the treatment arm and dose volume parameters. The correlation with acute toxicity and (pre-existing) bowel complaints was investigated. Patients and methods: 266 T1-4N0M0 prostate cancer patients were randomized for conventional (open fields) and 3D conformal radiotherapy using beams eye view blocked fields with the same dose (66 Gy) and gross target volume-planning target volume margin (15 mm). Apart from the RTOG toxicity scoring system a patient self-assessment questionnaire was used to obtain detailed information on morbidity. Results: At 2 years there is only a trend for less rectal toxicity (grade greater than or equal to 1) in favor of the conformal radiotherapy (grade 1, 47 versus 40% and grade 2, 10 versus 7% for conventional and conformal radiotherapy, respectively (P = 0.1). A significant relation was found between late rectal toxicity (grade greater than or equal to1) and the volume of the anus and rectum exposed to greater than or equal to90% tumor dose (TD). A highly significant relationship is observed between acute rectum and anal toxicity and late rectal toxicity, The patient self-assessment questionnaire analysis revealed that patients are most bothered by compliance related symptoms like urgency, soiling and fecal loss. In a multivariate analysis, all other variables loose significance, when anal volume exposed to greater than or equal to90% TD and pre-treatment defaecation frequency are accounted for. Late anal toxicity is low and related only to acute anal toxicity. Late bladder toxicity is related solely to pre-treatment frequency and overall urological symptoms. The incidence of grade 2 toxicity increases with a factor 2.5-4 when (stool or urine) frequency is unfavorable at the start of treatment. Conclusions: Conformal radiotherapy at the dose level of 66 Gy does not significantly decrease the incidence of rectal, anal and bladder toxicity compared to conventional radiotherapy. There is a significant relationship between acute and late toxicity and the anal volume exposed to 90% TD. Intestinal (and urological) symptoms at start have a major impact on late toxicity. (C) 2004 Elsevier Ireland Ltd. All rights reserved.