Background: The significant impact of postoperative radiotherapy (PORT) on cardiac morbidity in patients of early breast cancer (EBC) undergoing breast-conserving surgery has been shown in different studies. The present study was conducted to assess the impact of surgery and the side of involvement on radiation dose to left anterior descending artery (LAD) and Left circumflex coronary artery (LCx).
Materials and methods: Totally, 58 patients of EBC were randomly chosen for this dosimetric study and planned with tangential field technique without intensity modulation (IM). Heart, LAD, and LCx (n = 55) were contoured. Dose volume histograms were analyzed to determine the Dmax (maximum dose) and Dmean (mean dose) of LAD and LCx. Student's t-test was used for comparative analysis of the means.
Results: The mean Dmax of LAD for left (L) EBC was 3.17 Gray (Gy) while for right (R) EBC it was 0.86 Gy (P = 0.007; 95% C.I, 1.14-3.48). The mean Dmean of LAD for L-EBC and R-EBC were 1.97 Gy and 0.79 Gy, respectively (P = 0.029; 95% C.I, 0.77-1.60). The mean-Dmax of LCx for patients with L-EBC (2.9 Gy; range: 1.2-4.35 Gy) was statistically higher than that for R-EBC (1.3 Gy; range: 0.7-3.2 Gy) (P = 0.045). The mean-Dmean of LCx for L-EBC (2.1 Gy; range: 0.6-3.6 Gy) was also significantly higher than that of L-EBC (0.9 Gy; range: 0.7-2.1 Gy) (P = 0.03). There was no significant impact of the pattern of surgery on LAD dose, but significance was noted for LCx dose parameters (P = 0.04 and 0.08 for m-Dmax and m-Dmean of LCx).
Conclusion: This pilot dosimetric study confirms the assumption that patients with left-sided EBC are at higher risk of developing long-term cardiac morbidity when treated with PORT due to increased dose to LAD.