Risk of myocardial infarction and stroke after breast cancer: an analysis of a population of 1.3 million women from North-West Italy

Purpose: Breast cancer (BC) is a leading public-health issue affecting women on a global scale. Thanks to the widespread implementation of screening programs and the improvement in therapies, women with BC live longer but they also are more likely to experience an increased risk of other diseases. Reasons for this increased risk include genetics, shared risk factors, and adverse effects from BC treatment. Therefore, this research aimed to analyse the risk of myocardial infarction (MI) and stroke in women with BC, considering the potential side effects of treatments. Methods: For the analysis, we used data coming from the Piedmont Longitudinal Study (PLS), an administrative cohort based on the record-linkage among census data and several health-administrative databases involving more than 4 million inhabitants. The study population comprised women aged 30-75 years from the PLS study, excluding those with myocardial infarction or stroke at baseline. To analyse the investigated associations, competing risk analyses were performed, through the Cause-Specific Proportional Hazards model. Results: Among 1,342,333 women ranging from 30 to 75 years old, 19,203 had a BC diagnosis, of whom 206 (1.1%) experienced a subsequent MI and 203 (1.1%) a stroke. Women with BC showed an increased risk for MI (HR: 1.20; 95% CI 1.05-1.38) and for stroke (HR: 1.58; 95% CI 1.38-1.82). Chemotherapy was observed to be the major risk factor for MI in BC women, while no different risk by therapy was found for stroke. Conclusion: The results supported the hypothesis about the toxic effect of BC therapies, suggesting that clinicians should routinely and actively screen for treatment-related toxicities in women with BC and that researchers should prioritize personalized treatments to minimize potentially devastating side effects.