Left-sided Breast Cancer Radiotherapy and Risk of Heart Diseases: with Considering Baseline Risk of Heart Diseases

Introduction: Following breast conserving surgery, radiotherapy is used to control the tumor and increase the survival rates of patients. After radiation therapy, organ at risk, are prone to organ toxicity and secondary cancers. To compare the risk of heart disease in radiotherapy patients for left-sided in two treatment techniques of intensity modulated radiation therapy(IMRT) and three dimensional conformal radiation therapy(3DCRT) with considering blood factors, smoking, and underlying diseases. Method: 32 patients with left-sided breast cancer were used in the early stages were selected for this study. 3D-CRT and IMRT were planned to deliver prescribed dose to target volume. Schneider model was used to estimate excess absolute risk (EAR) of heart diseases, also10-years baseline risk of heart disease using Reynolds risk score for ages 50-70 years were calculated. Results: There was a significant difference in 10-year EAR of heart diseases when comparing 3D-CRT plans in IMRT (p<0.05). 10-year EAR for IMRT at low, median, and high risk groups were higher than 3DCRT. Among factors involved in baseline risk, by increasing the age, the impact of smoking on increasing EAR was clearer compared to the family history of heart disease. Conclusions: IMRT had a more uniform dose distribution and a better conformity-homogeneity index than 3DCRT. However, the mean heart dose and subsequently the risk of heart disease significantly were lower in 3DCRT. Adding risk factors which are effective in the development of heart disease can result in more accurate estimates of the risk of heart disease after breast cancer radiotherapy.