A COMPARATIVE STUDY OF DOSIMETRY AND SHORT-TERM TOXICITY BETWEEN CONVENTIONAL RADIOTHERAPY AND INTENSITY-MODULATED RADIOTHERAPY AFTER BREAST-CONSERVING SURGERY FOR EARLY BREAST CANCER
Objective To compare the dosimetry and the short-term toxicity between conventional radiotherapy and intensity-modulated radiotherapy (IMRT) after breast-conserving surgery for early breast cancer.Methods Eighty patients with early left breast cancer who received radiotherapy after breast-conserving surgery were randomly divided into conventional radiotherapy group and IMRT group.The acute radiation dermatitis,radiation pneumonitis,cosmetic effect,and radioactive myocardial injury were compared between the two groups.Thirty patients receiving IMRT were randomly selected to perform CT simulation to delineate the target volume and the organs at risk.The Eclipse 3D planning system was used to design the routine tangential field radiotherapy plan.The radiation dose distribution,uniformity index (HI),and conformity index (CI) of the target volume were analyzed and compared between the two groups using the dose distribution image of the planning target volume.The dose-volume histogram was used to compare the radiation dose and irradiation volume of the organs at risk (heart,lung,and contralateral breast) between the two groups.Results The IMRT group had significantly lower incidence rates of radiation pneumonitis,radiation dermatitis,and myocardial injury than the conventional radiotherapy group (z =3.672-5.098,P ＜0.05).There was no significant difference in cosmetic effect between the two groups (P＞0.05).After radiotherapy,the conventional radiotherapy group had significantly higher serum levels of C-reactive protein and troponin and incidence rates of ST-T segment abnormalities and arrhythmia than the IMRT group (t =2.173,2.784;x 2 =2.684,2.870;P ＜ 0.05).Compared with the conventional radiotherapy group,the IMRT group had significantly lower V100％ (percent volume receiving 100％ of the prescribed dose),V110％,and V115 ％,and significantly higher CI and HI (t =2.018-3.278,P ＜0.05).There was no significant difference in V95 ％ between the two groups (P ＞ 0.05).Compared with the conventional radiotherapy group,the IMRT group showed significantly lower V20,V30,and V40 of the ipsilateral lung and V30 and V40 of the heart,and significantly higher V2,V3,and V4 of the contralateral breast and V5 of the ipsilateral lung,the heart,and the contralateral breast (t=2.405-3.976,P＜0.05).Conclusion For patients receiving IMRT after breast-conserving surgery for early breast cancer,the dose distribution of the planning target volume has good conformity and uniformity and the radiation dose and irradiation volume of the organs at risk can be reduced significantly.IMRT can relieve the short-term toxicity of radiotherapy after the breast-conserving surgery for early left breast cancer.
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