The impact of breast cancer radiation therapy exposure on the prevalence of breast arterial calcification

Abstract

Objectives: Mammographic breast arterial calcification (BAC) is an emerging imaging biomarker of cardiovascular disease (CVD) risk in women. The purpose of this study was to assess if breast radiation therapy (RT) exposure impacts the screening utility of this imaging biomarker.

Methods: This cross-sectional study included women ages 40-75 years who underwent index screening mammography between January 1, 2011 and December 31, 2012. Chart review was performed to extract data on the breast cancer RT exposure and CVD risk factors. Mammograms were reviewed for the presence of BAC. Multivariate logistic regression was used to examine breast RT exposure and BAC, with adjustment for age, body mass index, smoking status, hypertension, Type 2 diabetes, statin medication use, and antihypertensive medication use.

Results: Of the 1155 women included in this analysis, 222 (19.2%) had mammographic evidence of BAC, 122 (10.6%) had a history of RT exposure, and 39 (32%) women with RT exposure had mammographic BAC. Women with breast RT exposure had higher odds of BAC compared to women without (odds ratio: 2.18, 95% CI: 1.43, 3.28; P-value = .0008). However, this association became non-significant after multivariable adjustment, with the maximally adjusted model demonstrating an odds ratio of 1.52 (95% CI: 0.95, 2.40; P-value = .07).

Conclusions: Our findings suggest that breast RT exposure does not impact the prevalence of mammographic BAC. Therefore, it does not affect its utility as an imaging biomarker of CVD risk.

Advances in knowledge: This is the first observational study addressing the knowledge gap pertaining to the influence of breast RT exposure on BAC.

Keywords: breast arterial calcification; cardiovascular disease risk; radiation therapy; radiotherapy; screening mammography.

Figure 1.

Study population. Flow diagram shows how the final analytic cohort was determined and reasons for exclusion.

Figure 2.

Bilateral cranio-caudal views demonstrating bilateral BAC (arrows) in 71 y/o patient with history of left breast invasive lobular carcinoma treated by wide local excision and radiation therapy (scar marker indicated by star). Mammogram obtained 4 years after RT completion consisting of 50.4 Gy to the left breast and a 10 Gy boost to the tumour bed. BAC is more extensive in the untreated right breast than in the left breast that received RT. Abbreviations: BAC = breast arterial calcification; RT = radiation therapy.