The Dosimetry Study On The Simultaneous X-ray And The Late Course Electron Boost Intensity Modulated Radiation Therapy For The Treatment Of Breast Cancer After Breast-conserving Surgery

Objective:To compare the dosimetry characteristics of X-ray synchronous boost intensity modulated radiation therapy and late course electron boost for breast cancer with/without tumor bed marking silver clips after breast-conserving surgery.Methods:Thirty female patients with right breast cancer received breast-conserving operation hospitalized in the third affiliated hospital of Kunming medical university between May 2012 to May 2014 were selected.15 patients’ tumor beds marked with silver clips, and the others were not. Radiotherapy plans for these patients were designed with X-ray simultaneous integrated boost intensity-modulated radiotherapy and simultaneous electronic lines boost intensity-modulated radiotherapy,respectively. Evaluate and compare differences on dosimetry of the target and organs at risk between the two groups.Results:1.Comparison of tumor beds marked with/without silver clips:1): Comparison of target volume:On tumor bed target volume and VCTV1/VCTV, the group without silver clip marks was obviously larger than the group with silver clip marks, there was significant difference between the two groups(P< 0.05); On whole breast target volume, the difference was not significant between the two groups. (P>0.05). 2). SIB-IMRT:There were significant differences on Dmin、Dmean、V95、V105、V110 of whole breast target volume between the two groups (P< 0.05); there were no significant differences on Dmax of whole breast target volume, homogeneity index and conformal index, Dmean of LTAT and Skin, dosimetry evaluation of endangered organ between the two groups (P>0.05).3).IMRT+E:There were significant differences on Dmean、V105、V110 of whole breast target volume and conformal index of tumor bed target volume between the two groups (P< 0.05); there were no significant differences on Dmax、Dmin、V95 of whole breast target volume, homogeneity index and conformal index of the whole breast, homogeneity index of tumor bed target volume,Dmean of LTAT and Skin, dosimetry evaluation of endangered organ between the two groups (P> 0.05).2. Comparison of SIB-IMRT and IMRT+E:1):with silver clip marks:There were significant differences on V20 of the right lung and Dmean of LTAT between the two groups(P< 0.05); there were no significant differences on dosimetry evaluation of target volume and endangered organs,homogeneity index and conformal index of the whole breast and tumor bed target volume,Dmean of Skin difference between the two groups (P> 0.05).2):without silver clip marks:There were significant differences on V10 of the right lung, V20 of the whole lung, V5、V15 of the heart and Dmean of LTAT between the two groups(P< 0.05); there were no significant differences on dosimetry evaluation of target volume and other endangered organs, homogeneity index and conformal index of the whole breast and tumor bed target volume,Dmean of Skin between the two groups (P> 0.05).Conclusions:Placing silver clip markers after breast-conserving surgery can reduce the irradiation dose and volume of endangered organs and tissues,postoperative radiotheraphy target volume and radiation injury of normal tissue. It’s helpful for precision radiotherapy with tumor bed marking silver clips after breast-conserving surgery. Simultaneous X-ray integrated boost intensity-modulated radiotherapy overall protection of the lungs,heart and the left breast was significantly superior to late course electronic lines boost intensity-modulated radiotherapy.