Dosimetric Comparison Of Intensity Modulated Radiotherapy And Three-dimensional Conformal Radiotherapy After Modified Radical Mastectomy For Breast Cancer

Objective : To investigate the dosimetric characteristics of chest wall,supraclavicular irradiation and organs at risks(lung,brachial plexus,and heart)in IMRT and 3D-CRT after modified radical mastectomy.Differences between the two groups.Methods A total of 24 patients with breast cancer received adjuvant radiotherapy after postmastectomy surgery,with a dose of 50 Gy in 25 sessions.Two different treatment plans,IMRT and 3D-CRT,were used to evaluate the relevant dosimetric parameters of the target and normal tissues.Finally,an independent t test was used to compare the dosimetric parameters of the two groups using SPSS 23.0 statistical analysis software.Results: The IMRT and 3D-CRT radiotherapy plans were designed respectively.The prescribed dose was 50 Gy in the chest wall target area,25 times,and 2 Gy each time.Comparing the two groups of planned target area conformity and organs at risk receiving capacity,IMRT not only significantly improved the conformity of the target area CI(0.77 vs 0.44,p = 0.000),but also significantly improved the target area homogeneity index HI(0.42 vs1.08,p =0.000).In terms of organs at risk,IMRT brachial plexus Dmax was lower than 3DCRT(53.27 Gy vs 55.57 Gy P= 0.000).IMRT brachial plexus Dmean was also lower than 3DCRT(39.55 Gy vs 42.65 Gy P=0.014);and IMRT significantly reduced high lung dose volume V20(25.94% vs 29.88%,p = 0.002)and did not reduce the low dose volume V5 of the affected lung(51.32% vs 47.73%;p = 0.029).The cardiac Dmean(6.91 Gy vs 7.64 Gy,p = 0.591)、V10(15.38±9.28 vs 15.50±13.50,p=0.979)、V20(12.47±8.36 vs 8.17±6.00,p=0.163),was not statistically significant.Conclusion : Compared with 3D-CRT,IMRT significantly improved the conformality and homogeneity of the target area.IMRT significantly reduces the high-dose volume of ipsilateral lung in terms of organ protection,but 3D-CRT is superior to IMRT in reducing low-dose volume.IMRT and 3D-CRT had no significant effect on cardiac Dmean 、 V10 、 V20.For brachial plexus,both IMRT and 3D-CRT can meet internationally-requested limits,but IMRT can control the dose of irradiation even lower.