WEDNESDAY, April 1 (HealthDay News) -- The cancer risk from computed tomographic (CT) scanning increases incrementally with repeated scans and should be part of the risk-benefit consideration for each patient, according to a report in the April issue of Radiology.
Aaron Sodickson, M.D., Ph.D., of Brigham and Women's Hospital in Boston, and colleagues analyzed records of 31,462 patients who had 190,712 CT exams over 22 years. The researchers estimated the cumulative radiation exposure for each patient, and then used the Biological Effects of Ionizing Radiation VII methodology to calculate the lifetime attributable risk for cancer. For patients with lifetime attributable risk greater than 1 percent, billing codes and electronic order entries were examined for evidence of cancer incidence.
The investigators found that 5 percent of the cohort had between 22 and 132 lifetime CT exams, and 33 percent had five or more. Fifteen percent of the cohort had radiation exposure in excess of 100 mSv, the level thought to increase cancer risk, and 4 percent received between 250 and 1375 mSv. The lifetime attributable risk for cancer incidence was a maximum of 12 percent and a mean of 0.3 percent; for cancer mortality, the maximum was 6.8 percent and the mean 0.2 percent, the researchers report. Of the 7.3 percent of patients in the cohort with lifetime attributable risk greater than 1 percent, 85 percent had a cancer history, and 40 percent had metastasis, the report indicates.
"Yet ultimately a risk-benefit decision must be made at the level of the individual patient and should involve balancing the highly context-dependent benefits of imaging against the patient-specific cumulative risks," the authors write.
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