OBJECTIVES: Measures are implemented to clinical practice to reduce the cardiotoxicity of breast cancer (BC) treatment. However, there is a lack of evidence regarding which cardiovascular diseases (CVDs) clinicians should monitor given a patient’s age. This study compares the cumulative incidence of eight CVDs in women with BC versus aged-matched controls by age at BC diagnosis.

METHODS: A case-control study was conducted using real-world data from the Cancer Registry of Norway, the Norwegian Patient Registry, the Norwegian Prescribed Drug Registry and the Norwegian Primary Care Registry. We created nationwide cohorts of women newly diagnosed with BC between 2013-2020 (cases) and age-matched controls. Index dates were defined as the first recorded date of BC diagnosis for the cases and a randomly selected date within the same year of the BC diagnosis for the matched controls (matching ratio 1:1). The two cohorts’ 4-year cumulative incidence of eight clinically relevant CVDs was compared, stratified by age at BC diagnosis (<60, 60-69, 70+ years).

RESULTS: Our study population consisted of 22,231 cases followed for up to eight years (<60 years: 11,036, 60-69: 6,363, 70+: 4,831). The difference in 4-year cumulative incidence between BC patients and controls significantly increased with age for hypertension (70+: 9.4% [CI 7.6%-11.0%] vs. <60: 2.5% [2.0%-3.0%]) and atrial fibrillation (70+: 3.3% [2.1%-4.6%] vs. <60: 0.2% [0.0%-0.4%]). For pulmonary embolism, the difference was significantly larger in the highest age group than in the middle (70+: 2.2% [1.5-2.9%] vs. 60-69: 0.8% [0.4-1.2%]). There were no significant differences across age groups for heart valve disease, heart failure, peripheral vascular disease, other cardiac arrythmias and ischemic heart disease.

CONCLUSIONS: Older women with BC have a relatively higher incidence difference (vs controls) of hypertension and atrial fibrillation than younger women with BC. This evidence may be crucial for personalizing BC therapy with respect to CVD.