A Comparison Of Toxicity And Dosimetry For Different Radiation Therapy Of Early-breast Cancer After Breast-conserving Surgery

Objective: To observe the acute radiation toxicity and cosmetic results of the early breast cancer after conserving surgery using 3-dimensional conformal radiation therapy with sequential boost(3D-CRT) or intensity modulated radiotherapy with simultaneous integrated boost(IMRT-SIB). At the same time to compare the difference of dose and volume in the organs at risk and target between 3D-CRT and IMRT-SIB.Methods: Collect the female patients who were early stage breast cancer after breast-conserving surgery between October 2012 and January 2016 in our department. The planning target volume’s dose of 3D-CRT group is 5000cGy/25 f, then using the electronic line plus the dose of 1000cGy/5f to the tumor bed. IMRT-SIB group was given the planning target volume’s dose of 5040cGy/28 f, simultaneous integrated boost to 6020cGy/28 f. Evaluate the acute radiation toxicity and cosmetic results of the different radiotherapy method. To selected 10 cases of left breast cancer patients in IMRT-SIB group, using the Oncentra treatment planning system to design 3D-CRT planning. Then compare the difference in dose distribution between the two treatment plan using dose-volume histograms.Results: There are 172 patients included in our study, 3D-CRT group has 82 and IMRT-SIB90. Follow-up to March 2016, differences in the two groups of acute radiation-induced skin reactions was statistically significant(p=0.001). The neoadjuvant chemotherapy(P=0.001)showed relationship with acute radiation skin reactions and age had not(P=0.063). The two groups all had excellent or good cosmetic outcome(p=0.313).Dosmetric comparision: ①The target volume:The difference in Dmax 、 Dmean between3D-CRT and IMRT-SIB group was statistically significant(p=0.009, p=0.017); The V100% 、V105%、V110% of IMRT-SIB group were lower than 3D-CRT group(p=0.037, p=0.001, p=0.04);The homogeneity index(HI) and the conformal index(CI) had the significant difference between the two group(p=0.028 、 p=0.001); ②The lung:The dose of ipsilateral lung were reduced in IMRT-SIB group, and the difference of V5, V10, V30 were statistically significant(p=0.020,p=0.024, p=0.001). V20 was not(p=0.373); ③The heart: In IMRT-SIB group, The V30, V40(p=0.04, p=0.01) of the heart were significantly lower than 3D-CRT group. The decline of V10 is not obvious. V5 was higher in IMRT-SIB group compared with 3D-CRT.Conclusion: The IMRT-SIB and IMRT could reduce the acute radiation-induced skin reactions incidence for patients who had breast conserving surgery compared with the 3D-CRT, all the three groups could get better cosmetic results. The IMRT-SIB group could improve the conformal index(CI) and homogeneity index(HI) in the left breast cancer and reduced the radiation dose and volume in ipsilateral lung、heart, but also increased the volume of low-dose in these organs.Conclusion: The IMRT-SIB group could reduce the acute radiation-induced skin reactions incidence for patients who had breast conserving surgery compared with the 3D-CRT. The two groups could get excellent cosmetic results. The IMRT-SIB group could improve the conformal index(CI) and homogeneity index(HI) in the left breast cancer and reduced the radiation dose and volume in ipsilateral lung、heart, but also increased the volume of low-dose in these organs.