According to a recent study, which included acute MI patients with no history of cancer from all over Quebec, low-dose radiation from cardiac imaging increases cancer risk.
Results of the study were published online in CMAJ and analyzed data of over 82,000 patients in the Quebec Med-Echo registry by Dr Mark Eisenberg (McGill University, Montreal, QC) and colleagues.
The registry documented all cardiac imaging and therapeutic procedures involving low-dose ionizing radiation and estimated the patients' exposure depending on the average effective radiation dose for that procedure, ranging from 15.6 mSv for myocardial perfusion screening down to 7 mSv for diagnostic cardiac catheterization.
A statistical analysis to adjust the patients' age, gender, and exposure to low-dose ionizing radiation from non-cardiac imaging discovered that for every 10 mSv of low-dose ionizing radiation a patient was subjected to increased risk of developing cancer within five years by 3%. Of the 82 861 patients involved in the cohort, 77% underwent at least one cardiac imaging or therapeutic procedure with low-dose ionizing radiation in the first year after an acute MI. The cumulative exposure to radiation from cardiac procedures was 5.3 mSv per patient-year, of which 84% was in the first year. The patients during the follow-up period were detected with a total of 12,020 incident cancers.
Cardiologists, radiologists, and patients are increasingly concerned about long-term impacts of the low-dose radiation exposure on patients subjected to some types of cardiac imaging procedures as mentioned by heartwire, especially patients likely to undergo multiple scans, such as MI patients. Moreover, Eisenberg et all's study appears to support the recent findings by Einstein et al that MI patients are subjected to a median of 15 procedures that expose them to radiation and about a third of these patients receive a total dose over than100 mSv.
Eisenberg et al reported "The potential increase in cancer-related death associated with exposure to radiation from cardiac imaging and therapeutic procedures has to be weighed against the potential risk of death from cardiovascular diseases for which these procedures are indicated and the resulting decrease in mortality expected with their use," But, this study is not sufficient show where the "balance between these competing risks falls" as it is relatively short and could have been affected by unknown confounding variables.
In addition, Mathew Mercuri (McMaster University, Hamilton, ON) and colleagues mentioned that "a strategy to track radiation doses may help physicians and patients stay aware of the cumulative exposure" Healthcare and nuclear industries have systems for controlling exposure to employees; however there isn't any national system for tracking exposure in patients.
