Purpose/Objective(s): The purpose of this study is to evaluate whether patients receiving adjuvant radiotherapy after breast cancer surgery have higher incidence rate of long-term coronary heart disease(CHD).

Materials/Methods: This is a retrospective cohort study. The national cancer registry database, health insurance datasets and death registry system were used. We identified 76,701 female with breast cancer (ICD-9: 174 or ICD-10: C50) diagnosed between JAN 2005 to DEC 2012. After excluded patients with incomplete information of cancer registry (n=19,852), diagnosed with any heart disease before index date (n=8,958), without surgery within 3 months after cancer diagnosed (n=1,230), and other exclusion criteria (n=9,309), there were 37,352 individuals followed from index date until occurrence of CHD(ICD-9: 410-414), death or end of study (DEC 2014). We further excluded patients receiving neoadjuvant or adjuvant chemotherapy(n=25866). The study individuals was then categorized into three different groups (including adjuvant radiotherapy, hormone therapy, and no adjuvant therapy) according to the first subsequently adjuvant therapy within 3 months after surgery. The multiple Cox regression model was used to estimate the adjusted hazard ratio (aHR) of CHD among study groups.

Results: A total of 4231 patients received adjuvant radiotherapy while 3819 patients received only hormone therapy. There were 3436 patients who received no further adjuvant treatment. The crude incidence rate (per 10,000 person months) of CHD were 6.32 (95% C.I.=5.45-7.32), 9.97 (95% C.I.=8.82-11.26), and 8.19 (95% C.I.=7.05-9.52) in adjuvant radiotherapy, hormone therapy, and no adjuvant therapy group , respectively. After adjusted age, clinical stage, socioeconomic status, and co-morbidities, the aHR (hormone therapy v.s. radiotherapy) was 1.17(0.89-1.54). There were no statistical significance among three different treatment groups.

Conclusion: The incidence rate of CHD is not significantly different between breast cancer patients receiving adjuvant radiotherapy, hormone therapy or without adjuvant treatment.