New research examining the 10-year mortality of patients after undergoing computed tomography (CT) exams may lead to a reevaluation of CT-associated radiation risks.
For the retrospective study, recently published in the European Journal of Radiology, researchers examined different radiation cumulative effective dose (CED) levels and 10-year mortality rates for 36,545 patients who had CT exams at a large tertiary care facility in 2013. The different CED groups included those who had 0 to < 10 mSv CED (group A:14,031 patients), 10 to < 50 mSv CED (group B:18,989 patients), 50 to < 100 mSv CED (group C: 2,756 patients) and > 100 mSV CED (group D:769 patients), according to the study.
The researchers noted significantly higher mortality rates at one and two years for groups D and C. Specifically, group D had a 6.7 times higher mortality rate at one year (23.5 percent) and a fivefold higher rate at two years (8.6 percent) in comparison to group A (3.5 percent and 1.7 percent respectively). Group C had a 4.3 times higher mortality rate at one year (15.2 percent) and a 3.9 times higher rate at two years (6.7 percent) in contrast to group A, according to the study authors.
However, the researchers found that the mortality rates peaked at year two across the groups with a noticeable decline in mortality rates afterward. At year 10, the study authors noted low equivalent mortality rates for groups D and B (0.5 percent), an 0.8 percent rate for group C and an 0.3 rate for group A.
The study authors emphasized that 37 percent of the group D cohort (who received > 100 mSV CED) were alive at 10 years and 48 percent of the group C cohort (who received 50 to < 100 mSv CED) were alive at 10 years.
“Based on this data, the argument that patients who receive radiation dose over 50 mSv are sick enough to die within a few years from prior diseases is unsound,” wrote lead study author Maria T. Mataac, an assistant researcher at Massachusetts General Hospital in Boston, and colleagues.
Three Key Takeaways
1. Higher mortality with increased CED. Patients with higher cumulative effective doses (CED) from CT exams (specifically groups C and D) had significantly higher mortality rates at one and two years compared to those with lower CED (group A). This suggests a correlation between higher radiation exposure and increased short-term mortality.
2. Mortality rates peak at two years. The mortality rates across all groups peaked at two years post-CT exams and then showed a noticeable decline. By the 10-year mark, the mortality rates were low and relatively similar across the groups, indicating that long-term survival might not be as adversely affected by higher CED levels as previously thought.
3. Reevaluation of radiation risks. The study challenges conventional views on the risk-benefit ratio of CT-associated radiation dosing. Despite the higher short-term mortality in groups with higher CED, a significant portion of patients in groups C and D were still alive after 10 years. This suggests that the assumption that patients receiving over 50 mSv are at a higher risk of dying from prior diseases may be unfounded, calling for a reevaluation of current radiation risk assessments.
Noting the potential risk for radiation-induced solid cancers and recent evidence suggesting the development of radiation side effects at CED levels below 100 mSv, the study authors said the current study’s findings challenge conventional notions about the risk-benefit ratio with CT-associated radiation dosing.
“Since significant portions of the patient population in Groups C and D are alive after 10 years, discussion on the current state of knowledge on radiation effects is appropriate,” maintained Mataac and colleagues.
(Editor’s note: For related content, see “AI-Based Denoising for Neck CT May Facilitate Reductions in Radiation Dosing,” “Could Virtual Non-Contrast Images from Photon-Counting CT Reduce Radiation Dosing with CCTA?” and “Can Deep Learning Bolster Image Quality with Low-Dose Lung CT?”)
Beyond the inherent limitations of a retrospective, single-center study, the authors emphasized the observational nature of the study and noted their findings do not show a direct link between mortality and radiation exposure from CT exams.
