Heart-protected Role of Left Ventricle as Organ at Risk in Postoperative Intensity Modulation Radiotherapy for Left-sided Breast Cancer with Breast-conserving Operation

Objective To study the role the left ventricle (LV) as a novel organ at risk (OAR) in postoperative intensity modulated radiotherapy (IMRT) for left-sided breast cancer patients who received breast conserved surgery (BCS) to protect the heart from unnecessary radiation. Methods The archived computed tomographic (CT) scans of 13 patients who received adjuvant radiotherapy (RT) in our department were selected at random for this dosimetric study.The same radiation oncologist contoured the clinical target volume (CTV) and OARs including lungs，the right breast，the heart and left ventricle (LV) and the same physicist did one tangential field (TF) pan and 3 IMRT plans.The prescribed dose (PD) was 50 Gy with 25 fractions.For the planning target volume (PTV) and OARs，the various dose-volume histogram (DVH) parameters were compared. Results Compared with TF plan，the maximal ［except for the IMRT (H)］and minimal doses increased differently.And Compared with IMRT(H) plan，the maximal dose and the volume higher than 110% of prescribed dose increased.Compared with TF plan，the mean heart dose，the median dose，V5，V10 increased 0.9%~22.3% (P>0.05),78.3%~110.6%(P<0.05),179.3%~209.2%(P<0.05),24.7%~97.7% respectively in all the IMRT plans.The maximal dose，V15，V20 decreased 18.6%~36.7% (P<0.05),7.2%~52.6%,48.3%~79.5%(P<0.05) respectively.For left lung，the high dose volume (>V17) decreased and the low dose volume (