Objectives/purpose: In Australian women, cardiovascular disease (CVD) is identified as a leading cause of death, with breast cancer the leading cancer diagnosis. While both CVD and breast cancer share common modifiable and non-modifiable risk factors, there are cardiotoxicity risks resulting from breast cancer treatment therapies. Adjuvant radiation therapy (RT) is an effective treatment for breast cancer, reducing the risk of local recurrence and improving survival. This study was designed to understand radiation dose distribution within the heart for patients receiving breast cancer RT comparing patients who had a CVD event post RT treatment with those who did not. Common shared risk factors including chemotherapy, diabetes and smoking status were also included, to understand their impact when considering dose to the whole heart and cardiac substructures.
Sample and setting: This retrospective study included seventy-two patients treated for left sided breast cancer at Radiation Oncology Princess Alexandra Hospital Ipswich Road, between 2002-2016.
Procedures: Cardiac structures including the whole heart, atria, ventricles and left anterior descending artery were contoured on the original patient treatment plans. The impact of dose, measure of heart in field (MHIF) and risk factors on the outcome of CVD post RT was investigated, using descriptive and exploratory statistics, inferential and predictor tests.
Results: Median MHIF measured 45 % greater for patients diagnosed with CVD (1.78cm vs 1.23cm (p=0.038)). Predictive analysis also showed MHIF (p=0.477), diabetes (p=0.244) and smoking (p=0.301), to be potential factors of influence for CVD after RT treatment.
Conclusions and clinical implications: Results suggested that MHIF and having diabetes or smoking may be factors of influence for a CVD event post RT treatment. Further examination of the relationships between dose to the cardiac substructures and the identified risk factors will inform protocols to moderate cardiac risks in future patients, positively impacting long-term quality of life.