Thirty-five studies (2,344 patients) were included in the review: 16 RCTs, 11 prospective cohorts, 3 retrospective studies, 2 qualitative studies, 1 feasibility pilot study and 2 case reports.
Dietary modifications during pelvic radiotherapy (18 studies).
One RCT (143 patients) of a low-fat dietary regimen found that the intervention was associated with a reduction in the incidence of diarrhoea in comparison with the control group: 1.1 versus 1.7 loose stools per week for the intervention versus the control group (p<0.01). Another RCT (21 patients) found a low-fat diet was associated with a significant reduction in the frequency of bowel motions: 1.6 and 2.0 bowel motions per day for the intervention and control groups, respectively (p<0.05). However, both studies suffered from methodological weaknesses. One RCT (190 patients) of probiotics found a significant reduction in grade 4 bowel symptoms (21.4% versus 0%), but significantly more grade 2 symptoms (65.3% versus 23.8%), for the intervention group compared with the control group. Another RCT (24 patients) of probiotics, found a significant reduction in the incidence of diarrhoea in the intervention group compared with the control group (18 to 27% versus 80 to 90%, respectively).
One RCT (680 patients) of an elemental diet intervention reported a lower level of grade 1 (16% versus 25%) and grade 2 (12% versus 27%) bowel toxicity in the intervention group compared with the control group. A phase two pilot study (17 patients) of an elemental diet also showed a reduction in the number and severity of diarrhoea days (5.9 versus 12.2 days, respectively; p<0.05). The remaining studies of elemental diets (2 RCTs and a prospective cohort study) failed to report a measure of bowel toxicity.
One RCT (56 patients) of an enzyme supplement found a reduction in moderate bowel symptoms in comparison with controls (57% versus 36%; p=0.01).
One retrospective study (156 patients) of a reduced residue regimen did not identify statistically significant differences in bowel symptoms.
Bowel toxicity was not reported in 3 studies (2 RCTs and 1 prospective cohort study) of protein or calorie supplementation, 1 RCT of micronutrient supplementation, 2 RCTs of parenteral nutrition and 1 RCT of a low lactose diet.
Dietary modifications after pelvic radiotherapy.
Two RCTs (246 patients) of probiotics did not report any improvements in chronic bowel symptoms.
One case report of an elemental diet noted resolution of symptoms for the patient. One crossover study (8 patients) of an elemental diet failed to report an objective measure of bowel toxicity.
A prospective cohort study (7 patients) of a low-fat dietary regimen reported moderate improvements in all patients. Another prospective cohort study failed to report an objective measure of bowel toxicity.
A gluten-free, cow's milk protein-free, low-residue, low-fat diet was reported to improve malabsorption and nutritional status in 5 case reports of children.
One case report found vitamin A to be beneficial for pain and signs of anal ulceration. One prospective cohort study (9 patients) of combined vitamins C and E resulted in the subsidence of symptoms after 6 to 12 weeks. Another prospective cohort study (20 patients) of combined vitamins C and E found that diarrhoea, urgency and bleeding resolved after 4 weeks. One prospective cohort study (20 patients) found magnesium supplementation resolved diarrhoea in patients with proctosigmoiditis.
Four cohort studies of parenteral nutrition and 2 qualitative studies of various self-imposed dietary changes did not report objective measures of bowel toxicity.