Kucuktulu, E., Guner, A., Kahraman, I., Topbas, M., & Kucuktulu, U. (2013). The protective effects of glutamine on radiation-induced diarrhea. Supportive Care in Cancer, 21(4), 1071–1075.

To investigate the protective effects of glutamine on radiation-induced diarrhea

Patients were divided into two groups. One group received 15 g oral glutamine each day beginning one week prior to radiotherapy and continuing until one week after radiation therapy completion. The other group was given an oral glucose solution.

• The study consisted of 36 patients with a mean age of 66 years.
• The sample was 62% male and 38% female.
• Renal, prostate, bladder, and gynecologic were the most common cancers.
• All were receiving radiation therapy in the range of 45–70 Gy. Some also had received concomitant chemotherapy with 5 fluorouracil (5FU) or cisplatin.

The study was conducted at a single outpatient site in Turkey.

Patients were undergoing the active treatment phase of care.

This was a two-group prospective trial.

• Patient diaries were used. 
• The National Cancer Institute (NCI) Common Toxicity Criteria (CTC), version 3.0, for diarrhea was used.
   

No between-group differences were found in overall incidence of diarrhea. None of the patients in the glutamine group developed grade 3–4 diarrhea, compared to 69% of those in the placebo group (p = 0.0000). More patients in the placebo group required loperamide and parenteral supportive therapy.

Findings suggest that oral glutamine may be helpful in the prevention and management of severe radiation-induced diarrhea.

• The sample size was small with fewer than 100 patients.
• A risk of bias exists because no blinding or random assignment was used.
• More patients in the placebo group received 5FU and had rectal cancer. 
• Diarrhea grading depends on patient recall of stool frequency, so reliability and accuracy may be questionable.
• The authors did not clarify how the criteria were applied and what toxicity value was used in analysis, because grading was apparently done twice weekly. 
• A 10% drop-out rate occurred because of a lack of compliance with the oral medication. 
• The glucose solution used as placebo was not well described. The nature of this solution could have worked as an osmotic laxative in the placebo group. 
• The authors did not explain how patients were assigned to study groups.

Findings suggest that oral glutamine may help in the prevention of severe radiation-induced diarrhea. However, study design issues limit the quality of this study. Use of glutamine warrants further investigation in large, well-designed randomized studies.