Planning Design And Comparison Of Different Radiotherapy Methods For Partial Breast Irradiation After Breast Conserving Surgery For Breast Cancer

Objective: The purpose of this study was to compare the difference between two different radiotherapy plans(Intensity-modulated radiotherapy and Tangential field radiotherapy)of partial breast irradiation,and to find a suitable radiotherapy plan for patients with early breast cancer after breast conserving surgery.Methods:This study has chosen 16 female patients.From June 2018 to February 2019,all of them were treated in the fourth Hospital of Hebei Medical University with radiotherapy after breast conserving operation.Siemens 64-slice spiral CT machine is used for positioning scanning.the CT scanning image is obtained and transmitted to Pinnacle planning system.The target area was delineated and audited by the same attending doctor and chief physician in our department,and then two groups of treatment plans were worked out by the same physicalist.The target dose,homogeneity index,conformity index,lung,heart and its substructure of the two groups were calculated.Analysis by SPSS20.0 statistical software.Result:Target dose distribution:95%of target volume of two plans all can reach the requirement of prescribed dose.The conformity index of the intensity-modulated radiotherapy group(0.712)was better than that of the tangent field radiotherapy group(0.594).The homogeneity index of the two groups was 0.090 and 0.083,but there was no significant difference between the two groups(P>0.05).OARs dose distribution:In the radiotherapy plan with tangent field radiotherapy,the Dmean,V5 and V10 of the affected lung tissue were lower than those of the intensity-modulated radiotherapy group.Stratified analysis showed that the Dmean,V5 and V10 of the intensity-modulated radiotherapy plan were significantly higher than those of the tangent field radiotherapy plan(P<0.05),and the difference was statistically significant in the intensity-modulated radiotherapy plan group than that in the tangent field radiotherapy group(P<0.05).Similarly,patients with lesions located in the left extra mammary quadrant came to a similar conclusion.However,when the lesion was located in the left breast quadrant,the results showed that only V5 in the intensity-modulated radiotherapy plan group was higher than that in the tangent field radiotherapy plan(P<0.05),and the remaining parameters were not statistically different.The Dmean and V5 of the group with the lesion located in the right breast were higher than those with the tangent field radiotherapy as the main plan,and the difference was statistically significant(P<0.05).However,further stratified analysis according to the quadrant of the patient’s lesions,the results were not statistically significant(P>0.05).There was no significant difference in cardiac dose parameters Dmax,Dmean and V5-V40 between the two plans.Stratified analysis showed that there was no significant difference in cardiac Dmax,Dmean and V5-V40 between the two groups when the lesion was located in the left breast,regardless of the internal and external quadrant(P>0.05).When the lesion was located in the right breast,the cardiac Dmean in the intensity-modulated radiotherapy plan group was higher than that in the tangent field radiotherapy plan group,and the difference was statistically significant(P<0.05).According to the stratified analysis of the quadrant where the lesion was located,there was no significant difference in the parameters between the internal and external quadrants(P>0.05).The levels of Dmean and V5 in the contralateral breast intensity-modulated radiotherapy group were higher than those in the tangent field radiotherapy group,and there was significant difference between the two groups(P<0.05).Conclusions:1.The target dose distribution of the intensity-modulated radiotherapy plan and tangent field radiotherapy plan can satisfy the requirements of clinical prescription dose.2.The conformity index of the intensity-modulated radiotherapy plan was better than that of the tangent field radiotherapy plan,but for homogeneity index,there was no significant difference between the two groups.Therefore,the intensity-modulated radiotherapy plan has a slight advantage over the tangent field radiotherapy plan in the target distribution of partial breast irradiation.3.Tangential field radiotherapy plan can reduce the average irradiation dose and the volume of low dose irradiation area in the contralateral lung and breast.For patients with right breast cancer,tangent field radiotherapy plan can also reduce the average dose of the patient’s heart and bring a better protection to the normal tissue structure.