Future radiation-induced cancer risk negligible in CT of acute TBIs

The lifetime attributable risk of cancer and cancer related mortality is negligibly increased by the radiation emitted from CT use in the evaluation and management of severe traumatic brain injuries (TBIs), according to a study published online Dec. 26 by the American Journal of Roentgenology. Decisions regarding radiographic evaluation in the acute treatment of TBI should not be influenced by concern regarding future risk of radiation-induced cancer.

Patients with TBIs undergo numerous CT studies during initial evaluation and hospitalization, raising concern about ionizing radiation exposure. This worry particularly pertains to pediatric patients, as they are more susceptible to radiation damage and cumulative dose exposure.

“Patients with TBI frequently receive large numbers of radiographic examinations during hospitalization; however, the degree to which this may augment their lifetime risk of cancer is unknown,” wrote the study’s lead author, Patrick N. Salibi, MD, of the University of Pittsburgh Medical Center, and colleagues.

The researchers investigated the lifetime attributable risk of cancer from CT among patients surviving severe TBI in their retrospective cross-sectional study. Sixty-seven participating patients were 16 years or older and admitted to a single level one trauma center from 2007 to 2010 with a Glasgow coma scale score of eight or less.

The effective dose of each CT examination underwent by patients was predicted by the study’s authors using literature-accepted effective dose values of standard helical CT protocols. Coupled with the approach established by the Biologic Effects of Ionizing Radiation VII report, the cumulative effective dose from the time of the injury to the one-year follow-up estimated the resulting lifetime attributable risk of cancer and related mortality from CT.

Results from the study revealed that the average patient was 34 years old and 81 percent of the population was male. During the first 12 months after injury, the median number of examinations undergone by each patient was 20. The average cumulative effective dose was 87 mSv. Unenhanced CT exams were the most common procedure performed but contributed 29 percent of the total cumulative effective dose.

The lifetime incidence of all cancer types increased from 45.5 percent to 46.3 percent and lifetime incidence of cancer-related mortality negligibly increased from 22.1 percent to 22.5 percent. The researchers determined that approximately 183 patients with severe TBI would have to be exposed to similar cumulative effective doses before one patient contracted cancer attributable to CT exams.

Though women had a slightly greater lifetime attributable risk of cancer than men, the difference was not statistically significant. Participants younger than 40 had significantly higher lifetime attributable risk of cancer and death than older patients.

Most of the study’s limitations stemmed from the utilization of models for risk estimation, wrote the authors. The lifetime attributable risk of cancer and related mortality were not based on actual epidemiologic data of malignancy rates after modern CT. However, conducting risk assessment in this way would necessitate a long follow-up time.