NUTRITIONAL SUPPORT DO NOT PREVENT GI TOXICITY DURING RADIATION 

NEW YORK (Reuters Health) May 10 - Little high-grade evidence supports nutritional interventions to counteract acute gastrointestinal toxicity during therapeutic pelvic radiotherapy, researchers from the UK report.

Treatment-induced toxicity of noncancerous tissues limits the dose of pelvic radiotherapy for gynecological, urological, and lower gastrointestinal malignancies, with up to 90% of patients experiencing symptoms of varying severity.

To explore one option for preventing radiation-induced GI toxicity, Dr. H. J. N. Andreyev from The Royal Marsden NHS Foundation Trust, London, UK, and colleagues conducted a comprehensive review of the potential benefit of nutritional manipulation during radical pelvic radiotherapy.

They included 22 original studies involving 2,446 patients in their study, as reported April 23 online in Alimentary Pharmacology and Therapeutics.

Only six studies scored high on the quality analysis. Among the 16 randomized controlled trials included in the analysis, only nine reported favorable outcomes for the intervention. Seven showed no difference or worse outcomes.

Six studies (836 patients) investigated the use of elemental nutritional formulas. Evidence for their efficacy was weak, and the authors doubted whether 100% replacement of normal diet with elemental formula could be achieved during long-course radiotherapy.

Low- or modified-fat diets were tested in four randomized controlled trials with 316 patients. Two high-quality trials provided limited evidence of their efficacy, but neither study manipulated fat as the sole intervention, the researchers note, "making it difficult to determine which intervention was responsible for efficacy."

The use of dietary fiber also had only weak support, with inconclusive results from four studies (including two randomized controlled trials, neither of them high-quality) involving 275 patients.

Lactose restriction (three studies, 118 patients) did not prove helpful, despite limited evidence that patients can become lactose-intolerant during pelvic radiotherapy.

Five randomized clinical trials (901 patients) provided only limited evidence for the efficacy of probiotics in reducing acute diarrhea in this setting.

"Of all nutritional interventions in this review, probiotic supplementation appears to offer the most promise as a prophylactic for positively influencing toxicity outcomes," the authors note. "However, our knowledge about the precise mix of dynamic and diverse microbiota that inhabits the human gastrointestinal tract is still limited and is highly individual."

"Attempting to manipulate such an ill-defined ecosystem should be approached with caution especially as our methods of analyzing the effects of such supplementation on incumbent microbiota are still relatively crude outside the research setting," they say.

"There is insufficient high-grade evidence to recommend any of the nutritional interventions in this review be implemented in clinical practice," the investigators conclude.

Dr. Andreyev did not respond to a request for comments on this report.

Dr. Alfonso Vidal from Complejo Asistencial Universitario de Leon, Spain, who was not involved in the study, did agree to comment on it. "I have been happily surprised by the selection of the analyzed interventions in the review as many of them - like modified diet or elemental enteral nutrition- are not usually discussed," Dr. Vidal told Reuters Health by email. "Few high quality surveys have been developed during the last years, and the results of the review encourage (us) to improve the methodology of research in this area."

Dr. Vidal, who has studied possible interventions for preventing acute radiation enteritis, added, "Some points should be clarified regarding the use of probiotics, like the useful strains, the required dose, or the association of prebiotics. N-3 fatty acids could focus the interest of investigators in the future, as some animal studies suggest that these nutrients can play a dual role in radiotherapy - protecting normal tissue and boosting the cytotoxic effect on tumor cells."

SOURCE: http://bit.ly/ZUhhM8

Aliment Pharmacol Ther 2013.