Association of cancer treatment with excess heart age among five-year young breast cancer survivors.

[PURPOSE] Data evaluating cardiovascular disease (CVD) risk by cancer treatment among young women (≤ 40 years) with breast cancer are limited.

[METHODS] Among 372 five-year breast cancer survivors aged 30-40 years from the Young Women's Breast Cancer Study, we assessed the association of cancer treatments (anthracyclines, trastuzumab, radiation/laterality, endocrine therapy) and excess heart age (difference between predicted 10-year CVD risk as assessed by adapted Framingham Risk Score and chronological age), prevalent elevated excess heart age (≥ 2 years), and worsening excess heart age (change of ≥ 2 excess heart age years) at breast cancer diagnosis and two- and five-year follow-up using multivariable linear and logistic regressions.

[RESULTS] Most women had stage I or II (79%), ER + (71%), or PR + (65%) breast cancer. At diagnosis, women had little excess heart age by treatment receipt (range of means = -0.52,0.91 years). Left-sided radiation (β = 2.49,SE = 0.96,p = 0.01) was associated with higher excess heart age at five-year follow-up. For prevalent elevated excess heart age (two-year = 26%;five-year = 27%), women treated with right-sided radiation had increased risk at two-years (OR = 2.17,95%CI = 1.12-4.19), yet at five-years, associations were observed after any radiation (OR = 1.92,95%CI = 1.09-3.41), especially after left-sided (OR = 2.13,95%CI = 1.09-3.41) radiation. No associations were observed between systemic treatments and prevalent elevated excess heart age or any treatments with worsening excess heart age.

[CONCLUSIONS] Among young breast cancer survivors, radiation, but not other cancer treatments, was associated with elevated excess heart age.

[IMPLICATIONS FOR CANCER SURVIVORS] CVD risk tools that incorporate cancer treatment, such as radiation, are needed to identify high risk young breast cancer survivors given the long survivorship and long latency of cardiovascular disease.