A new method to decrease the cardiac radiation dose in postoperative radiotherapy for breast cancer-Anterior myocardial territory as an independent organ at risk
Objective To investigate the feasibility of anterior myocardial territory(AMT) as an independent organ at risk(OAR) in postoperative intensity modulated radiotherapy(IMRT) for left-sided breast cancer patients who received breast conserved surgery(BCS) to avoid unnecessary cardiac radiation. Methods The archived computed tomographic(CT) scans of 23 patients who received adjuvant radiotherapy were selected randomly for this dosimetric study. The same radiation oncologist delineated the clinical target volume(CTV) and OARs including both lungs, the right breast, the heart, left ventricle(LV), AMT and the same physicist designed two IMRT plans including IMRT(H+LV) and H(AMT) plan. The prescribed dose(PD) was 50Gy with 25 fractions. For the planning target volume(PTV) and OARs, the various dose-volume histogram(DVH) parameters were compared with paired t-test. Results For the PTV, the homogeneity index, conformity index, and coverage index of both IMRT plans were not different statistically. Compared with IMRT(AMT), The maximal dose to AMT increased significantly and mean dose to AMT increased without statistical difference(P =0.069), the V12Gy, V13Gy, V15Gy, V17Gy and V20Gy increased 15.37%, 18.87%, 26.48%, 27.11% and 26.04% respectively(P <0.05), and the V5Gy, V7Gy, V8Gy and V10Gy of LV did 4.21%、16.72%、20.91%and 19.14%(P <0.05). All the dose-volume parameters of the heart and LV as well as majority of the dose-volume parameters of right lung and breast were not different statistically. Conclusion For left-sided breast patients with breast conserved surgery,anterior myocardial territory replaced the heart as an independent OAR may decrease the cardiac dose in the postoperative radiotherapy.
Breast cancerIntensity modulation radiation therapyLeft ventricleOrgan at riskCardiac complication
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