15-year prospective follow-up of patient-reported outcomes of late bowel toxicity after external beam radiotherapy for localized prostate cancer. A comparison with age-matched controls

We have previously described patient-reported outcomes of late side effects induced by conventional external beam radiotherapy (EBRT), 4 and 8 years after treatment, in 181 patients with localized prostate cancer compared with 141 agematched controls. In the present study, we compare bowel side effects 15 years after EBRTwith the same controls, and with the results of our previous 4-year and 8- year follow- ups. Of the 181 patients and 141 controls at the 4-year follow-up, 45 patients (25%) and 79 controls (56%) were still alive at the 15-year follow-up. Bowel symptoms were assessed using the symptom- specific questionnaire Prostate Cancer Symptom Scale (PCSS), which was sent to these 45 patients and 79 agematched controls with a mean follow- up time of 15 years (162-197 months) after EBRT. The answer frequency was 64% in the patient group and 52% in the control group. The mean age was 78 years in both groups. At the 15-year follow-up, 39% of the patients and 84% of the controls reported no bowel problems (p < 0.001), while 16% of the patients and 0% of the controls reported "Quite a few/many'' problems with mucus in the stools (p < 0.001). "Quite a bit/much'' stool leakage was reported by 20% of the patients at the 15-year follow-up, in comparison to 4% of the patients at the 4-year follow-up (ns). The proportion of patients reporting late bowel symptoms was unchanged 15 years after EBRT in comparison to the 4-year follow-up. Increased bowel symptoms were seen in patients in comparison to the age-matched controls.