ESTRO 2021 Abstract Book

S444

ESTRO 2021

dose left vs right for each substructure was tested by Mann-Whitney test.

Results A total of 17,088 BC patients were included (left: 8,757 (51%), right: 8,331 (49%)). At median 7.3 years (IQR: 4.8-10.1) follow-up, 277 (1.6%) patients developed CAD (left: 134 (1.7%), right: 143 (1.5%), p=0.34). The incidence rate ratio (IRR) of CAD in left- vs right-sided patients was 0.89 (0.70-1.13). For 190 patients with subsequent CAD, CT data was available (left: 91 patients, Right: 99 patients). In > 90% of these, mean heart dose (MHD) was < 2.50 Gy. The median MHD was 1.00 Gy (IQR: 0.67-1.59) for all patients and 1.50 Gy (0.83- 2.14) and 0.82 Gy (0.58-1.18) for left- and right-sided patients, respectively (p <0.001). The distribution of CAD was not associated with laterality of RT (fig 1). The dose distribution, left vs right to the cardiac substructures was statistically significantly different for all relevant cardiac substructures. However, the dose difference, left minus right, was < 2.00 Gy, except for the middle and distal part of left coronary artery (fig 2).

Conclusion In a cohort of modern treated early BC patients, significant difference in RT doses to the heart and cardiac substructures was observed. However, no increased risk of CAD in left vs right-sided patients was detected at median 7 years follow-up. Thus, for patients treated with 3D-CRT in our cohort, RT dose to the heart was of no clinical importance for developing CAD.