Effects of a dietary intervention on gastrointestinal symptoms after prostate cancer radiotherapy: long-term results from a randomized controlled trial

To evaluate the long-term effects of dietary intervention on gastrointestinal symptoms after highly dose-escalated radiotherapy for localized prostate cancer, using boost with protons or high-dose-rate brachytherapy.

Patients were randomized to an intervention group (n=64) advised to reduce insoluble dietary fiber and lactose intake, or to a standard care group (n=66) advised to continue their usual diet. Gastrointestinal symptoms, other domains of health-related quality of life (HRQOL), and dietary intake were evaluated for ⩽24months post-radiotherapy with the European Organization for Research and Treatment of Cancer quality-of-life questionnaires QLQ-C30 and QLQ-PR25, Gastrointestinal Side Effects Questionnaire, and Food Frequency Questionnaire. The effect of the intervention on gastrointestinal symptoms was evaluated using generalized estimating equations.

Dietary intervention had no obvious effect on long-term gastrointestinal symptoms or HRQOL. The intervention group markedly reduced their dietary fiber and lactose intake during radiotherapy, but adherence tended to decline over time. The vast majority of long-term gastrointestinal symptoms were reported as 'a little', with a noticeable difference from pre-treatment only for unintentional stool leakage, limitations on daily activities, and mucus discharge.

Long-term gastrointestinal symptoms were predominantly mild, and dietary intervention was not superior to a usual diet in preventing these symptoms.