Cancer risk related to gastrointestinal diagnostic radiation exposure.

Exposure to ionizing radiation is associated with an increased risk of cancer. With the growing use of diagnostic imaging studies, there is concern for increasing the risk of radiation associated malignancy of the gastrointestinal tract. The purpose of this review is to summarize the existing literature for risk of gastrointestinal malignancy after ionizing radiation exposure from diagnostic imaging studies. Estimates of organ specific effective doses of radiation vary widely based on the method of measurement and patient factors. Most of the current data are based on calculations of organ effective doses from anthropomorphic phantoms and estimated cancer risk based on radiation exposure from environmental sources. Radiation associated cancer risk is dependent on both the cumulative radiation dose and the radiosensitivity of the particular organ. The majority of radiation exposure and risk associated with gastrointestinal malignancy comes from CT scans, especially of the abdomen/pelvis. Of the abdominal organs, the colon carries the highest lifetime attributable risk of radiation associated malignancy. The attributable risk of malignancy for an individual diagnostic imaging study is low, but measurable, and therefore imaging studies without radiation such as MRI and ultrasound should be considered, especially in patients who require repeated imaging studies. There is a shortage of epidemiological data and an absence of prospective data with adequate follow-up to describe accurate risk estimates of gastrointestinal cancers after diagnostic imaging. More studies are needed to better determine the risks of malignancy from diagnostic imaging.