The proportion of patients getting lower levels of exposure also increased. About 2.2 percent of the earlier cohort received cumulative doses between 50 and 100 mSv, compared to 4.2 percent of the later group.

Based on their models of radiation's effect on the body, the authors estimated about 0.3 percent of excess cancer in the earlier group, and 0.4 percent in the later group, could be attributed to ionizing radiation from CT scans. This works out to estimates of 1,659 cancers for the 1998-2001 cohort, and 2,185 in the 2002-2005 cohort.


However, most of these estimated cancers come from including the under 50 mSv group. Looking at just patients with cumulative doses 100 mSv or above, the researchers calculated about 72 cancers in the earlier and 183 in the later cohort.

The researchers noted some limitations with their study. They only had Medicare claims data to analyze, so they couldn't examine the appropriateness of studies. Also, because they were dealing with the Medicare population, they weren't able to extrapolate risk to younger patients, who have more to fear from excess radiation exposure, partly because of the typical 15-year lag time to develop radiation-induced cancers, the researchers said.

The study is "Exposure to Ionizing Radiation and Estimate of Secondary Cancers in the Era of High-Speed CT Scanning: Projections From the Medicare Population."

Back to HCB News

More Industry Headlines