No association between tumor laterality and cardiac-related mortality in breast cancer patients after radiotherapy: a population-based study

Abstract

Wei-Hua Li,1 Zi-Guan Zhang,1 Zheng-Rong Huang,1 Wei Zhang,1 Zhi-Bin Li,2 Zhong-Quan Qi3 1Xiamen Institute of Cardiovascular Diseases, The First Affiliated Hospital of Xiamen University, Xiamen 361003, People’s Republic of China; 2Epidemiology Research Unit, The First Affiliated Hospital of Xiamen University, Xiamen 361003, People’s Republic of China; 3Organ Transplantation Institute, Medical College, Xiamen University, Xiamen 361005, People’s Republic of China Introduction: To assess the effect of tumor laterality to cardiac-related deaths of breast cancer in the current radiation practices using a large modern population-based study.Methods: Women diagnosed with breast cancer from 2000 to 2008 were included using the current Surveillance, Epidemiology, and End Results database. The primary outcome of this study was the cardiac-related mortality. Multivariate analysis was performed using the Cox proportional hazards model to analyze the cardiac-related mortality including demographic, clinicopathologic, and treatment factors.Results: We identified 168,761 breast cancer patients, including 85,006 (50.4%) patients with left-sided tumors and 83,755 (49.6%) patients with right-sided tumors. The median follow-up period was 8.8 years. The 10-year cardiac-related mortality was 2.3% and 2.3% in left- and right-sided tumors, respectively (P=0.685). The results indicated that patients with older age, non-Hispanic Black, receipt of mastectomy, and married status were the independent adverse factors for cardiac-related mortality. However, left-sided tumors were not associated to a higher risk of cardiac-related mortality than right-sided tumors following postoperative radiotherapy (right vs left, hazard ratios 1.025, 95% CI 0.856–1.099, P=0.484). The risk of cardiac-related mortality in the entire cohort was increased with the extension of follow-up time. However, there was still not significantly different between left- and right-sided tumors. Subgroup analysis also found no association between tumor laterality and cardiac-related mortality after postoperative radiotherapy based on various demographics and treatment factors.Conclusion: With a median follow-up of 8.8 years, no significant differences were found in cardiac-related mortality between left- and right-sided tumors under current radiation practices of breast cancer patients. Keywords: breast cancer, radiotherapy, tumor laterality, cardiac mortality

Keywords

• Breast cancer
• radiotherapy
• tumor laterality
• cardiac mortality