A Comparison Of Dose Parameters For Early Stage Breast Cancer After Breast-conserving Surgery Using Four Different Radiotherapy Techniques

Objective:A comparison of dose parameters for early stage breast cancer after breast-conserving surgery using four different radiotherapy techniques.Methods:Fifteen patients with left side breast cancer were treated with conservative surgery followed by radiotherapy. After target definition, the treatment planning was performed by conventional tangential wedge-based fields (TW), field-in-field intensity-modulated radiation therapy(FIF-IMRT), tangential inverse planning intensity-modulated radiation therapy (T-IMRT) and volumetric modulated arc therapy (VMAT) respectively on the same CT scan. The PTV dose was prescribed with50Gy and V47.5≥95%. Same dose constraint was used for all four plans. The target dose distribution, the irradiation doses and volumes for the heart, coronary artery, lung and contralateral breast were read in the dose volume histogram (DVH), which compared for four different radiotherapy techniques. The monitor units were also compared.Results:Four plans were able to meet the V95%. The dose conformity index of TW, T-IMRT, FIF-IMRT and VMAT were1.69±0.7,1.37±0.1,1.45±0.0和1.02±0.0respectively, VMAT improved significantly the dose conformity index of target volume (CI, P<0.05), as compared with TW, FIF-IMRT and T-IMRT. The dose homogeneity index of TW, T-IMRT, FIF-IMRT and VMAT were0.15±0.3,0.11±0.1、0.11±0.3和0.09±0.2respectively, VMAT and T-IMRT improved significantly the dose homogeneity index of target volume (HI, P<0.05), as compared with TW, FIF-IMRT. VMAT increased the V5%, V10%and V20%of organs at risk (heart and ipsilateral lung), but didn’t increase V30%. VMAT increased significantly the V4%, V5, V10%and Dmean of coronary artery, and the irradiation doses of right breast and right lung, with statistical significance. T-IMRT and FIF-IMRT decreased significantly the irradiation doses of heart, coronary artery, lung and contralateral breast. The MU of TW, T-MRT, FIF-IMRT and VMAT were395±90、390±53、250±14和672±86respectively, VMAT decreased significantly MU (P<0.05), as compared with TW, FIF-IMRT and T-IMRT.Conclusion:A comparison of four radiotherapy plans for early stage breast cancer after breast-conserving surgery, VMAT improved significantly CI and HI of target volume, increased the irradiation doses of normal tissues and MU, prolonged the treatment time; T-TIMRT and FIF-IMRT improved CI and HI of target volume, decreased the irradiation doses of organs at risk.