Cardiovascular disease (CVD) is the second most common cause of death in breast cancer patients. Certain adjuvant treatments (e.g. anthracyclines, radiotherapy) increase the risk of CVD, in particular in patients with pre-existing CVD risk factors. Early identification of these patients enables targeted cardioprotective interventions, and switching to less cardiotoxic treatments. The strongest independent CVD risk factor is the presence and amount of coronary artery calcium (CAC). In clinical practice, CAC is quantified on cardiac CTs. Breast cancer patients treated with radiotherapy routinely undergo planning CTs. These inferior quality CTs may give the opportunity to routinely assess CAC.