Were We Able to Reduce Cardiac Doses in Breast Cancer Radiotherapy Over Time?

Abstract

In this study, we aimed to review the heart and left coronary artery doses over the years in patients who received breast cancer radiotherapy (RT). A total of 436 breast cancer patients of 2 RT centers treated between the years 2010 and 2018 were included. The mean heart doses (HeartDmean-HDM) and left coronary artery mean doses (LDM) were analyzed using nonparametric tests. The conventional RT (CRT) was 50 Gy/2 Gy in 5 weeks, and the hypofractionated RT (HRT) was 40.05 Gy/2.67 Gy in 3 weeks. Boost was applied as 10-16 Gy/2 Gy for CRT and 10 Gy/2.5 Gy for HRT. An equivalent conventional total dose of 2 Gy/fraction (EQD2) was taken into account for HRT. HDM was 107±104 cGy, and LDM was 288±209 cGy for the entire group. HDM was significantly lower in patients with breast-conserving surgery (99±94 cGy) than that in those with mastectomy (128±124 cGy) (p<0.001). Field-in-field intensity-modulated RT technique significantly reduced the doses compared to volumetric applications (104±95 cGy vs 141±38 cGy; p = 0.002). HDM was significantly increased with lymphatic RT (132±58 cGy vs 112±115 cGy; p<0.001). The addition of internal mammary volumes significantly increased HDM (p<0.001). No significant effect of boost was observed (p = 0.96). For both CRT and HRT regimens, HDM values were significantly lower after the year 2014 (right side p<0.001, left side p = 0.01). In the left side CRT, HDM was 1.74 Gy before 2014 and 1.3 Gy after 2014 and 1.0 and 1.19 Gy, respectively, for the right side. All efforts to reduce the cardiac doses will likely reduce long-term side effects.