Plasma samples were collected from male participants enrolled in a cross-sectional prostate cancer and pelvic radiotherapy study (Microbiota-and radiotherapy-induced gastrointestinal side-effects, MARS, study; London-Bromley Research Ethics Committee (REC) no. 13/LO/1527) . A subset of this pilot study, consisting of 285 plasma samples, were provided for metabolic profiling. After collection, plasma samples were stored at -80°C prior to their analysis.