Impact of Gastrointestinal Side Effects on Patients’ Reported Quality of Life Trajectories after Radiotherapy for Prostate Cancer: Data from the Prospective, Observational Pros-IT CNR Study

SIMPLE SUMMARY: The analyses presented, based on data from the PROState cancer monitoring in ITaly from the National Research Council (Pros-IT CNR) study, evaluated patients’ reported quality of life outcomes related to bowel function and bother over a 2-year period from the diagnosis. Growth mixture models were considered for patients who underwent radiotherapy, including treatments that were associated or not associated with androgen deprivation therapy. Our data revealed that the proportion of patients that were radiotherapy-treated with persisting significant bowel worsening at the 24 months interval is very limited. The absence of comorbidities and the use of intensity or volumetric radiotherapy techniques with image guidance were found to be related with a better tolerance to radiotherapy in terms of bowel side effects. These findings could be relevant for treatment selection and accurate patient information. ABSTRACT: Radiotherapy (RT) represents an important therapeutic option for the treatment of localized prostate cancer. The aim of the current study is to examine trajectories in patients’ reported quality of life (QoL) aspects related to bowel function and bother, considering data from the PROState cancer monitoring in ITaly from the National Research Council (Pros-IT CNR) study, analyzed with growth mixture models. Data for patients who underwent RT, either associated or not associated with androgen deprivation therapy, were considered. QoL outcomes were assessed over a 2-year period from the diagnosis, using the Italian version of the University of California Los Angeles-Prostate Cancer Index (Italian-UCLA-PCI). Three trajectories were identified for the bowel function; having three or more comorbidities and the use of 3D-CRT technique for RT were associated with the worst trajectory (OR = 3.80, 95% CI 2.04–7.08; OR = 2.17, 95% CI 1.22–3.87, respectively). Two trajectories were identified for the bowel bother scores; diabetes and the non-Image guided RT method were associated with being in the worst bowel bother trajectory group (OR = 1.69, 95% CI 1.06–2.67; OR = 2.57, 95% CI 1.70–3.86, respectively). The findings from this study suggest that the absence of comorbidities and the use of intensity modulated RT techniques with image guidance are related with a better tolerance to RT in terms of bowel side effects.