Objective:To investigate the dosimetric difference between three hypofractionated intensity-modulated radiotherapy（IMRT） techniques in tumor target volume and normal tissue

since hypofractionated radiotherapy is one of the recommended regimens after modified radical mastectomy for breast cancer

and to provide a basis for the planning and design of clinical radiotherapy. Methods:A total of 22 patients after modified radical mastectomy for breast cancer received CT simulation

and the target volume was delineated on CT simulation images with reference to the RTOG suggestion for target volume delineation after modified radical mastectomy for breast cancer. The heart（left and right ventricles and atria）

the ipsilateral and contralateral lungs

and the contralateral breast were defined as organs at risk. The IMRT planning system was used for each patient to plan and design partly fixed-jaw dynamic IMRT

jaw-tracking dynamic IMRT

and jaw-tracking static IMRT

and the prescribed dose was 40.05 Gy/15 fractions for the chest wall and the supraclavicular and infraclavicular regions. Dose-volume histogram and number of monitor units were used to compare the dosimetric difference between the three plans. Results:The IMRT plans obtained by the three techniques met clinical requirements. Pairwise comparison showed that there were no significant differences in the evaluation parameters D50 and D98 of planning target volume. The P-fixed-D group（partly fixed-jaw dynamic IMRT） had the highest number of monitor units

followed by the P-unfixed-D group（jaw-tracking dynamic IMRT） and the P-unfixed-S group（jaw-tracking static IMRT）

and there was a significant difference between groups（P < 0.05）. The P-fixed-D group had the highest conformity index. For the organs at risk

there were no significant differences in V30 of the heart and Dmaxof the spinal cord between groups（P > 0.05）

and compared with the other two groups

the P-fixed-D group had significant reductions in V5 of the ipsilateral lung

Dmeanof the heart

and Dmeanof the contralateral breast（P < 0.05）. Conclusion:Partly fixed-jaw dynamic IMRT reduces the exposure dose to organs at risk and maintain conformity index and homogeneity index of planning target volume within a reasonable and acceptable range

and therefore

it is recommended to be used in the planning and design of hypofractionated IMRT after modified radical mastectomy for breast cancer.