A study published ahead of print in The American Journal of Cardiology has found that after cardiac imaging and procedures, women have a higher risk of incident cancer than men. However, their absolute risk of cancer is low and they should still undergo these interventions because the benefits outweigh the risks.
Patrick Lawler, Department of Medicine, Divisions of General Internal Medicine, Cardiology, and Clinical Epidemiology McGill University, Montreal, Canada, and others comment that, in a previous study, they found an association between low-dose ionising radiation (LDIR) exposure from medical cardiac imaging and procedures after a myocardial infarction and subsequent risk of malignancy. As studies have also shown that women are at increased risk of incident cancer after exposure to LDIR compared with men, Lawler et al aimed to see if women were at increased risk of cancer associated with LDIR exposure after myocardial infarction. “We hypothesised, based on the findings from previous studies, that women would be at greater relative risk,” they state.
Using a population-based longitudinal cohort, the authors identified patients who been undergone some form of cardiac imaging or procedure involving LDIR exposure (myocardial perfusion imaging, diagnostic cardiac catheterisation without intervention, cardiac catheterisation with percutaneous coronary intervention, and cardiac resting ventriculography/multiple gated acquisition scan). They excluded all patients who had received with some form of cancer diagnosis or had been seen by an oncologist prior to entry to the cohort or within one year afterwards. Also as studies indicate a five-to-10 year latency between LDIR exposure and cancer development, Lawler et al subtracted a three-year time lag from the time of cancer of diagnosis to exclude all radiation within the three years preceding the cancer diagnosis. This meant data from 6,934 new cancers (from 82,861 patients; 56,606 men and 26,255 women) were available for analysis.
Overall, women had slightly less mean LDIR exposure in the first year after myocardial infarction than men (14.6±14.4mSv vs. 16.8±14.4 mSv, respectively). However, Lawler et al report: “For each millisievert of cardiac LDIR, women were more likely to develop a cancer than men after adjusting for age, non-cardiac LDIR, and other covariates (p for interaction=0.014).” Women also had a significantly greater risk of cancers of the thorax, which was mainly driven by a greater risk of incident bronchogenic cancers.
However, according to the authors, the relative risks for each sex are small and “the absolute risk difference on a population level would be expected to be very small”. They add that the benefits of cardiac imaging and procedures that involved LDIR exposure probably outweigh the risks, commenting: “Clinicians should be very wary of deferring useful interventions for fear of LDIR risk, doing so only when procedures are truly unnecessary or when alternative non-LDIR-emitting technology is available.”
Study author Louise Pilote, professor of Medicine, James McGill Chair, director, Division of General Internal Medicine, McGill University and McGill University Health Centre, Montreal, Canada, tells Cardiovascular News: “As we gain more information on diagnostic and therapeutic procedures in cardiology, we learn that the risks and benefits often differ between men and women. Enough women must be enrolled in large studies so we apply gained knowledge appropriately in each sex.”