Postmastectomy electron beam chest wall irradiation(EBCWI) in patients with breast cancer

Objective:To find out the dosimetry characteristic of EBCWI in postmastectomy patients with breast cancer for rational application in clinical practice.Methods:This study was base on CT images of 10 postmastectomy patients with left breast cancer,and with the use of Eclipse 8.6 3D-TPS(matching with Varian Clinac iX accelerator).Clinic target volume(CTV),lungs and heart were confirmed by senior radiotherapy doctors,treatment plans were designed to simulate BCWI using different irradiation energy from different gantry angles.Dose distribution and DVH were evaluated.Furthermore,boluses were used for more ideal results.Results:Better dose distribution and higher mean dose of CTV(CTVmean) occurred in EBCWI plans by 20°-40°gantry angles.The prescription of 50 Gy gave to 95%CTV,was unable to be achieved by 6MeV electron beam;When using 9 MeV,12MeV and 15MeV electron beam,volume of ipsilateral lung received ≥20Gy(LungV20) were 31%±6%,50%±4% and 65%±8%,and volume of heart that received ≥30Gy(HeartV30) were 10%±2%,23%±3% and 38%±5%,respectively;Irradiation dose of lung and heart had reduced obviously by excelsior boluses application while CTV dose had little change.Conclusion: EBCWI by energy between 9MeV and 12MeV from about 30° ipsilateral gantry angle are better selection in postmastectomy patients with breast cancer.And boluses should be correctly applied to optimize dose distribution.