Incidental Coronary Artery Calcification on Simulation Breast Radiotherapy Imaging and Risk of Subsequent Ischemic...

As survival after early-stage breast cancer improves, competing health risks such as ischemic heart disease (IHD) are increasingly relevant. Coronary artery calcification (CAC) is a validated marker of coronary atherosclerosis and is frequently visible on non-contrast CT. Radiotherapy simulation CT may offer an opportunity to detect subclinical coronary atherosclerosis in asymptomatic patients.

A retrospective cohort study was conducted including patients aged ≥65 years undergoing adjuvant radiotherapy for early-stage breast cancer. CAC was visually assessed on simulation CT using a three-level score: 0 (none), 1 (mild focal calcification), and 2 (extensive calcification). The primary endpoint was incident IHD during follow-up. Associations were evaluated using exact logistic regression. A survey of radiation oncologists assessed current reporting practices.

A total of 207 patients were included, with a mean follow-up of 6.6 years. Six patients (2.9%) developed IHD. CAC was absent in 89 patients (43%), mild in 60 (29%), and extensive in 58 (28%). All ischemic events occurred exclusively in patients with extensive calcification (6/58, 10.3%) and none with lower scores (0/149 patients, 0%). Extensive CAC was associated with increased risk of IHD (odds ratio (OR) 22.8, p=0.0008). Among patients without pre-existing IHD (n=189), the association remained robust (OR 17.45, p=0.006; age-adjusted OR 18.47, p=0.008). Notably, although patients with known IHD had a greater calcification burden overall, 4 of 6 events occurred in patients without known cardiac history, all with extensive CAC. Across 32 surveyed radiation oncologists, only 12.5% reported routinely documenting CAC, while 78.1% indicated willingness to modify practice if clinical relevance were established.

Extensive CAC on breast radiotherapy simulation CT is strongly associated with subsequent IHD but is infrequently reported in clinical practice. Incorporating structured assessment into routine reporting may improve cardiovascular risk stratification and preventive care.