Effect of a Low-FODMAPs Diet (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols) on Gastrointestinal Symptoms , Quality of Life and performance status in Cancer Patients Receiving Abdominal and pelvic Radiotherapy: An Interventional Study

This study aims to investigate the effect of a low-FODMAP diet on gastrointestinal symptoms and quality of life in cancer patients receiving radiotherapy to the abdominal and pelvic regions.

Pragmatic, community based, parallel group, randomised controlled trial

Initially, a list of eligible patients will be obtained from the radiotherapy center, and a demographic information form will be completed for each patient. Then, the low-FODMAP diet will be explained to patients in the intervention group, and the relevant dietary instructions will be provided to them. Patients will be divided into two groups: an intervention group, which will receive the low-FODMAP diet from the start of radiotherapy for 5 weeks and up to 2 weeks after completion of treatment, and a control group, which will continue their usual diet. Quality of life will be assessed using the EORTC QLQ-C30 questionnaire, and patients’ performance status will be evaluated at the beginning, during, and at the end of radiotherapy. Finally, quality of life, gastrointestinal symptoms, and performance status will be compared between patients adhering to the low-FODMAP diet and those following their usual diet.

Inclusion Criteria Consent to participate and ability to complete study procedures Histopathologically confirmed cancer Candidate for radical or adjuvant radiotherapy Adequate renal, hepatic, and bone marrow function Exclusion Criteria Refusal to participate Prior radiotherapy Severe active disease, including IBS Distant metastatic cancer

Low-FODMAPs Diet (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols)

Assessment of gastrointestinal symptoms, quality of life, and performance status in cancer patients receiving radiotherapy to the abdominal and pelvic regions

Randomization Procedure In this study, after assessing the eligibility criteria and obtaining written informed consent, participants will be randomly allocated into two groups: the intervention group (receiving the Low-FODMAP diet) and the control group (usual diet). 1. Type and method of randomization: This study will use simple randomization with a 1:1 allocation ratio. A random number table will be used to generate the random allocation sequence. 2. Unit of randomization: The unit of randomization is the individual participant (patient). Each eligible participant, after enrollment and assignment of an identification code, will be allocated to one of the two study groups. 3. Tool and method for generation of the random sequence: The random allocation sequence will be generated by a person who is not involved in participant recruitment or eligibility assessment, using a random number table. For each participant number, group assignment will be determined based on the selected random number (e.g., odd/even numbers corresponding to one of the two groups). The final randomization sequence will be prepared and documented before the start of the study. 4. Allocation concealment: To prevent selection bias, the random allocation sequence will be placed in sequentially numbered, opaque, sealed, and non-transparent envelopes. At the time of enrollment, the researcher will open only the next envelope in sequence, and the participant will be assigned to the corresponding group according to the card inside the envelope. Therefore, the researcher will remain unaware of the group assignment until the envelope is opened. 5. Stratified randomization: Stratified randomization will not be used in this study, and all participants will undergo simple randomization without stratification.