Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences (CAMS) and Peking Union Medical College (PUMC), Beijing 100021,China
Abstract：Objective To investigate the dosimetric characteristics of conventional two-dimensional radiotherapy of the chest wall,supra-and infra-clavicular regions,and the incidental irradiation dosage of the internal mammary region after modified mastectomy in breast cancer patients. Methods Clinical data of 20 breast cancer patients including 10 left and 10 right cases who received radiotherapy after modified mastectomy between 2015 and 2016 were retrospectively analyzed. All patients received irradiation to the chest wall,supra-and infraclavicular regions at a prescription dose of 43.5 Gy in 15 fractions with conventional technique. One anterior-posterior (AP) photon field irradiation was delivered for the supra-and infra-clavicular regions,and one electron field for the chest wall. The supra-and infraclavicular regions were re-planned by using two AP/PA fields and the doses of organ at risk were evaluated. Results With conventional radiotherapy,the D90 of the supra-and infra-clavicular regions were more than 39.15 Gy (EQD2≥45Gy) in 17 patients (85%),and the median D90 of the chest wall was 35.38 Gy. The median dose of incidental internal mammary region was 13.65 Gy. Patients with lower body mass index (BMI) received higher D90 in both supra-and infra-clavicular and chest wall irradiation (P=0.039,0.347). Conclusions Irradiation at D90 of 39.15Gy to the supra-and infra-clavicular regions with AP/PA fields can meet the prescription dose requirement of ≥90% in most cases and does not increase the irradiation dose to normal tissues. The dose distribution of one electron field of the chest wall is poor. Incidental internal mammary region can be irradiated at a limited dosage. BMI is an influencing factor for dose distribution.
Zhai Yirui,Wang Shulian,Tang Yu et al. Dosimetric evaluation of conventional two-dimensional radiotherapy after modified mastectomy for breast cancer patients[J]. Chinese Journal of Radiation Oncology, 2019, 28(9): 696-700.
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2019, Vol. 28 
