Millions of Americans undergo CT scans as a routine screening in diagnosing a variety of medical problems. A CT (computed tomography) scan, commonly called a “cat” scan, is a special type of X-ray that gives a detailed view of scanned areas to help doctors make diagnoses. A CT scan, like other X-rays, exposes the patient to some radiation. Recent studies are suggesting that amount of radiation may be too much, leading to a higher risk of cancer for some patients.

The numbers of CT scans performed each year in America is increasing with about 68.7 million performed in 2007 compared to 62 million in 2006. Although CT scans are an extremely useful tool for doctors, is it worth the increased risk of cancer for the patients? The results of two studies published in the current issue of the Archives of Internal Medicine, point to an increase of concern for patients who have undergone numerous CT scans in their lifetimes. The cumulative effect of the radiation can increase the risk of cancer to levels above the lifetime attributable risk (LAR) baseline of 42%. While the LAR varies widely for everyone based on the other risk factors in their life.

The studies included over 31,000 people and looked at those who had undergone several CT scans in their lives. About one-third of the study group members had received 5 or more lifetime CT scans, 5% of the group had more than 22 lifetime scans and 1% had over 38 CT exams. The risk of cancer from the accumulated exposure to radiation was increased by 1% to as much as 12% for those in the highest risk categories of the group.

While newer CT scanners use less radiation than older machines, most of the currently used machines emit a significant amount of exposure to patients. The studies suggest that as many as 14,500 deaths will result from cancers caused by the 68.7 million CT scans done in the year 2007 and from each individual year of testing. Approximately 2/3 of the cancers are expected to be found in women, including approximately 2000 breast cancers.

Many doctors believe the benefits of CT scanning far outweigh the risks associated with exposure to radiation and advocate for no change in the frequency of use of the scan. While CT scans are without question useful tools, it also extremely likely that many of the scans could be eliminated without danger to patients. Patients, especially those who have already undergone more than three or four CT scans, should discuss the potential dangers with their doctors before consenting to the treatment.