Changes Of The Dose Of PTV And Normal Organs In IGRT For22Patients With Breast Cancer

Objective:To investigate the changes of the dose of PTV and normal organs in image-guided radiotherapy for breast cancer using cone-beam computed tomography imaging and replanning. Methods:This study enrolled22patients with breast cancer after breast-conserving surgery who were treated by image-guided radiotherapy using CBCT technology in our hospital from June2012to December2013. IGRT plan was designed before therapy when we could get the dose volume histograms. The differences between the position and the reference coordinates were obtained before the11th treatment through CBCT scanning. We gained (X, Y, Z) a and (X, Y, Z) b values using online computer automating and manually mating to calculate to get DVHa and DVHb, which were using to compare with the primal DVH. The differences between the two plans were gained when we compared the exposure dose of lung, heart and Contralateral breast. Results: Compared with the original plan, PTV minimum dose of plan a is lower than original plan (P=0.012) and target minimum dose of plan b is lower than original plan (P=0.007). The radiation dose of the90%PTV volume (D90) in plan a is significant higher than the original plan (P=0.000) and D90in plan b is also higher than the original plan (P=0.000).Conclusions:IGRT applied to the breast cancer patients after breast-conserving surgery is with dosimetric advantage. Offline adaptive radiation therapy can significantly improve the target dose. The CBCT online verification system has little systematic error to be worth generalization at clinical.