Myocardial infarction patients who undergo cardiac imaging and other procedures might have an increased risk of cancer from the accompanying low-dose radiation, according to a new study.
Authors of the study, which appears in the current issue of the Canadian Medical Association Journal, note that CT angiography and nuclear scans have increased in frequency, leading to questions about possible health concerns. In some healthcare facilities, those procedures have replaced tests that do not involve radiation such as echocardiography and stress tests on treadmills with increasing frequency.
For the study, researchers from the McGill University Health Centre and the Jewish General Hospital in Montreal examined data from 82,861 patients who had heart attacks between 1996 and 2006 with no history of cancer. Of those patients, 77% underwent at least one cardiac procedure involving low-dose ionizing radiation within a year of their attacks.
We found a relation between the cumulative exposure to low-dose ionizing radiation from cardiac imaging and therapeutic procedures after acute myocardial infarction, and the risk of incident cancer, wrote Dr. Louise Pilote, researcher in epidemiology at the Research Institute of the MUHC and director of the Division of Internal Medicine at the MUHC, with coauthors. Although most patients were exposed to low or moderate levels of radiation, a substantial group were exposed to high levels and in general tended to be younger male patients with fewer comorbidities.
The median age of patients was 63.2 years, and 31.7% were women. Patients whose treating physicians were cardiologists had higher levels of exposure to radiation compared with those whose treating physicians were general practitioners. There were 12,020 incident cancers detected during follow up, with two-thirds of the cancers affecting the abdomen/pelvis and chest areas.
These results call into question whether our current enthusiasm for imaging and therapeutic procedures after acute myocardial infarction should be tempered, the authors wrote. We should at least consider putting into place a system of prospectively documenting the imaging tests and procedures that each patient undergoes and estimating his or her cumulative exposure to low-dose ionizing radiation.
In a commentary that ran with the study, Mathew Mercuri, McMaster University, and coauthors wrote that, although the radiation exposure of many tests is often low, the frequency with which such tests are performed may pose a population risk.
Possible solutions include using procedures with lower or no radiation exposure, especially in the case of multiple procedures. The commentators also propose tracking radiation doses to give patients and physicians a better idea of the risk of cumulative exposure.