Diet and Gastrointestinal Symptoms in Patients with Prostate Cancer Treated with Radiotherapy

Sammanfattning: Objective The main objective of this thesis was to explore the effects of diet on gastrointestinal symptoms in prostate cancer patients treated with local curative radiotherapy, by evaluating dietary intake prior to treatment (Study I), the psychometric properties of a new questionnaire on patient-reported gastrointestinal side effects (Study II), and the effect of a dietary intervention on acute and long-term gastrointestinal symptoms up to 2 years after radiotherapy completion (Study III-IV).Methods A total of 130 men with localized prostate cancer referred to dose-escalated radiotherapy (ED2 87-102 Gy, ?/?=3 Gy) were recruited to a dietary intervention trial. Patients were randomized to receive either standard care plus the dietary intervention of a fibre- and lactose-restricted diet (intervention group, IG; n=64) or standard care alone (standard care group, SCG; n=66). Data on gastrointestinal symptoms and dietary intake were collected pre-treatment and at seven time points during a follow-up period of 26 months.Results Prior to treatment, grain products and milk products were major sources of energy. Unbalanced fatty acid intake and low intake of selenium were observed (Study I). Validation of the Gastrointestinal Side Effects Questionnaire (GISEQ) revealed satisfactory internal consistency, moderate concurrent validity and adequate responsiveness (Study II). There were no significant effects of the intervention on acute or long-term gastrointestinal symptoms, but a tendency towards lower prevalence and severity of bloating and diarrhoea in the IG compared to the SCG during radiotherapy. Gastrointestinal symptoms were predominantly mild, and the frequency of clinically relevant symptoms was merely a few percent. Dietary adherence in the IG was initially good, but tended to decline beyond 12 months post-radiotherapy (Study III-IV).Conclusions A fibre- and lactose-restricted diet was not superior to the habitual diet in reducing gastrointestinal symptoms in patients undergoing high-dose, small-volume radiotherapy for localized prostate cancer. The GISEQ enables assessment of patient-perceived change in symptoms, but further work is needed to strengthen its psychometric qualities. It is suggested that continued research in this area target patient categories referred to irradiation of larger pelvic volumes with a higher risk of gastrointestinal symptoms, and that dietary interventions incorporate established strategies to enhance adherence and effectiveness.