Radiation and the small intestine. Future perspectives for preventive therapy.

Radiotherapy continues to enjoy a prominent role in the treatment of certain human tumors. Unfortunately, the undesired effect of radiation upon normal intestinal tissue often limits its therapeutic potential. While there is abundant information on the effects of radiation on the morphology of the intestine and on the proliferative process which occurs in the intestinal crypts, there is a paucity of information on the early and late effects of sublethal doses of radiation upon the absorptive functions of the intestine. The intestinal epithelium has a rapid turnover rate and is highly radiosensitive. Radiotherapy for malignant human neoplasms is a relatively safe and effective form of treatment, but it may become limited by its undesired side effects upon the gastrointestinal tract. A variety of clinical tests have been suggested as potential indicators of impending intestinal damage, but there is little information on the time course of radiation damage and the associated impairment of intestinal function. Such basic information is essential to assess early functional changes and to thereby allow for the development of suitable clinical tests to allow for the prediction of impending intestinal damage. Provision of this information to the radiotherapist would permit alterations to the timing or dose schedules of radiotherapy and would allow continued treatment, while avoiding or reducing unwanted side effects. In recent years, there has been extensive research on radiation injury to small intestine. This article will review some of the progress in this field, and will focus on potential future therapy to prevent or treat radiation damage to the intestine. These agents include WR-2721, enprostil, vasopressin, defined-formula diets and alterations in the ratio of dietary polyunsaturated-saturated fatty acids.