71 Background: To evaluate the incidence of late fecal incontinence (linc) after high-dose radiotherapy (RT) in prostate cancer patients (pts) accrued in AIROPROS 0102 trial (RT doses: 70-80Gy, 1.8-2Gy/fr) and to model the relationship between linc and clinical/dosimetric factors. Methods: Self-reported questionnaires of 515 pts with a minimum follow up of 6 yrs were analyzed with respect to linc. G1 linc was scored if unintentional stool discharge was “sometimes” experienced, G2 linc if unintentional stool discharge was “often” experienced or if pts sporadically used sanitary pads; G3 if pts reported daily unintentional stool discharge or use of sanitary pad >2 times/week. Correlation between pre-treatment morbidities, hormonal therapy, drug prescription, presence of diabetes or hypertension, abdominal surgery prior to RT (SURG), presence of G2-G3 acute fecal incontinence (ACUINC), pelvic nodes and seminal vesicles irradiation, mean rectal dose, dose-volume histograms constraints (from V20Gy to V75Gy) and linc was investigated by uni- and multivariate (MVA) logistic analyses. 347/515 pts had at least 3 toxicity questionnaires in the first 36 mos after the end of RT. Correlation between the mean score of fecal incontinence in the first 36 mos and linc at 6 yrs was also investigated. Results: 50/515 G1, 3/515 G2 and 3/515 G3 linc were reported. In MVA, V40Gy (continuous variable, p=0.09, OR=1.015), use of antihypertensives (protective factors, p=0.005, OR=0.38), SURG (p=0.004, OR=4.7), presence of haemorrhoids (p=0.008, OR=2.6) and ACUINC (p=0.007, OR=4.4) resulted to be correlated to linc. Based on MVA results, a nomogram was developed. Linc at 6 yrs was also correlated to the mean incontinence scores in the first 36 mos (p<0.0001): pts without linc at 6 yrs had a mean score of 0.1 during the first 36 mos, while pts with G1 and with G2-G3 linc at 6 yrs had a mean score of 0.5 and 0.78 during the first 36 mos, respectively. Conclusions: Mean score for incontinence during the first 36 mos after RT can be used as a surrogate endpoint for late (>6yrs) fecal incontinence. Linc is correlated to clinical and dosimetric risk factors and individualised toxicity prediction can be performed through a nomogram.
Incidence of late rectal bleeding in high-dose conformal radiotherapy of prostate cancer using equivalent uniform dose–based and dose–volume–based normal tissue complication probability models
