RESUMEN
Objective@#To compare the dosimetric parameters of target volumes and organs at risk between volumetric-modulated arc therapy (VMAT) and intensity-modulated radiotherapy (IMRT) for left sided breast cancer after breast-conserving surgery by a meta-analysis.@*Methods@#Literature search was performed to include related studies to analyze the dosimetric parameters of target volumes and organs at risk.@*Results@#A total of 11 studies involving 154 patients were included in meta-analysis. There were no significant differences in Dmean, HI of PTV-Whole breast and PTV-Boost. Comparing to IMRT, VMAT increased the conformity index (CI) of PTV-Whole breast (P=0.000) and PTV-Boost (P=0.002). When the mean volume of target volumes was≤634 cm3, there were no significant differences in Dmean, V5, V20 of the heart and left sided lung, V30 of the heart, Dmean of the right sided lung and breast between VMAT and IMRT.When the mean volume of target volumes was>634 cm3, the Dmean(P=0.037), V5(P=0.005) and V20(P=0.030) of the heart in IMRT was lower than VMAT, but the V30(P=0.001) of heart in VMAT was lower than IMRT.IMRT showed significantly lower Dmean(P=0.013), V5(P=0.000), V20(P=0.000) of the left sided lung, and Dmean(P=0.001) of the right sided lung than VMAT.There were no significant differences in Dmean of the right sided breast.@*Conclusions@#There were no significant differences in dosimetric parameters of target volumes between VMAT and IMRT.When the mean volume of target volumes was≤634 cm3, there were no significant differences in dosimetric parameters of organs at risk. When the mean volume of target volumes was>634 cm3, IMRT has some advantages in protection of the heart and lung.
RESUMEN
Objective We developed a method to expand margin of beam aperture for VMAT treatment planning of breast cancer and evaluated its effectiveness in clinic. Methods An expanded VMAT (E-VMAT) plan for breast cancer using Pinnacle39. 10 planning system was made. A small tissue-equivalent bolus was added at the middle of the breast surface as part of the target and the VMAT plan was generated with beam aperture automatically expanded. Then the tissue-equivalent bolus was removed and the final dose distribution was calculated. Ten patients with breast cancer undergoing breast conserving surgery were tested. The dosimetrical metrics and delivery efficiency were compared between the E-VMAT plans and the routine VMAT plans. Results On the BEV view, it was observed that in E-VMAT plans the collimator and MLC leaf positions was extended outside the skin along the anterior-posterior direction of the thorax. There were no significant differences in conformity index and homogeneity index of target volume between the two types of plans and the planned delivery efficiency was consistent (P>0. 05). Conclusions The method established in this study can automatically generate expansion of VMAT beam apertures and prevent missing of target volume due to respiratory motion and/ or setup error of the patient. The method does not require programming skill and available for different treatment planning systems.