Risk of Heart Disease in Left-Sided Breast Cancer Radiotherapy: With Considering Baseline Risk of Heart Diseases

After lumpectomy, radiation therapy is used to control the tumor and increase patient survival. Following radiation therapy, the organs at risk are vulnerable to toxicity and secondary cancer.
Thirty-two patients with early-stage of left breast cancer were selected for this study. Intensity-modulated radiotherapy (IMRT) and three-dimensional conformal radiotherapy (3DCRT) were planned to deliver the prescribed dose to the target volume. Considering baseline risk of heart disease, the excess absolute risk (EAR) of heart disease was calculated using the Reynolds risk score for ages 50-70.
There was a significant difference in 10-year EAR of heart disease when comparing 3DCRT plans to IMRT (p <0.05). The 10-year EAR for IMRT in the low, median, and high-risk groups was superior to 3DCRT.  Among factors involved in baseline risk, by increasing the age, the impact of smoking on increasing EAR was clearer compared to a family history of heart disease. 
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. Considering baseline risk leads to accurate estimates of the heart disease risk after breast cancer radiotherapy.