Association Between Thoracic Radiotherapy and Severity of Coronary Artery Calcification in Lung Cancer: A Retrospective Cohort Study

Objective To investigate the association between thoracic irradiation (TIR) and the severity of coronary artery calcification (CAC) in patients with lung cancer, and to provide evidence-based basis for cardiovascular risk stratification and early intervention in lung cancer patients undergoing radiotherapy. Methods A retrospective cohort study design was adopted. A total of 126 patients with primary lung cancer who received thoracic radiotherapy in the oncology department of a tertiary hospital from January 2018 to December 2023 were consecutively enrolled as the radiotherapy group, and 126 lung cancer patients diagnosed during the same period but without radiotherapy were matched at a 1:1 ratio as the non-radiotherapy group. Propensity score matching was performed for baseline characteristics including age, sex, smoking history, hypertension, diabetes, dyslipidemia and tumor stage. The CAC score was semiquantitatively calculated by the Agatston method based on follow-up chest CT images obtained at least 12 months after radiotherapy, and the severity was classified into three grades according to the number of involved vessels: no calcification, single-vessel calcification and multi-vessel calcification. Dosimetric parameters of the radiotherapy group were collected, including mean heart dose (MHD), heart V30 and left anterior descending artery (LAD) dose. Inter-group differences were compared using t-test, χ2 test and rank-sum test. Multivariate ordinal Logistic regression was used to analyze the independent influencing factors of CAC severity. Results The median CAC score in the radiotherapy group was significantly higher than that in the non-radiotherapy group [426.3 (IQR: 118.5–982.7) AU vs. 187.6 (IQR: 42.3–563.2) AU, Z=-4.215, P<0.001]. The proportion of multi-vessel calcification in the radiotherapy group was significantly higher than that in the non-radiotherapy group (46.0% vs. 27.0%, χ2=10.286, P=0.006). Multivariate ordinal Logistic regression analysis showed that after adjusting for age, hypertension, diabetes, dyslipidemia and smoking history, thoracic radiotherapy was an independent risk factor for increased CAC severity (OR=2.87, 95%CI: 1.64–5.02, P<0.001). In the subgroup analysis of the radiotherapy group, MHD≥10 Gy (OR=2.31, 95%CI: 1.12–4.76, P=0.023) and LAD maximum dose≥35 Gy (OR=2.05, 95%CI: 1.03–4.08, P=0.041) were independently associated with more severe CAC. Conclusion Thoracic radiotherapy in lung cancer patients is independently associated with increased severity of coronary artery calcification, and patients with higher cardiac radiation dose tend to have greater CAC severity. Routine baseline CAC assessment before radiotherapy, optimization of cardiac dose constraints during treatment, and strengthened cardiovascular event monitoring and early intervention during follow-up are recommended.