A Preliminary Study On The Relationship Between The Different Dose Volumes Of Ipsilateral Lung With Radiation-Induced Pulmonary Fibrosis In Patients With Breast Cancer Treated By VMAT After Modified Radical Mastectomy

Objective:To analyze the correlation between different dose volume of ipsilateral lung with radiation-induced pulmonary fibrosis(RIPF)after Volumetric Modulated Arc Therapy(VMAT)that followed with modified radical mastectomy of left breast cancer.And to explore the clinical and dosimetric risk factors of RIPF,so as to provide a certain dosimetric basis for the prevention of RIPF in patients with breast cancer radiotherapy.Methods:Through retrospective analysis of patients with left breast cancer,who were treated in our department from January 2016 to December 2018,all patients were treated by modified radical mastectomy,then accepted supraclavicular combined with thoracic wall regions radiotherapy by VMAT radiotherapy techniques.Initially 226 patients were included,then the patients who met the following conditions were further selected:the total dose of radiotherapy was 50 Gy/25f,200cGy/f/d,5f/W,dexamethasone was used during radiotherapy or within 1 month after radiotherapy,and regular reexamination was performed in our hospital after radiotherapy,including chest CT examination.The clinical data of patients was collected age,menopause,underlying diseases,tumor location(left breast,quadrant),lesion size,surgical methods(modified radical resection),disease staging(TNM staging),Pathological diagnosis(pathological type,histological grade,intravascular tumor thrombus),molecular typing(Her-2,ER,PR),chemotherapy regimen and course of treatment,targeted drug therapy and endocrine therapy,the dosimetric parameters(V5?V30 and MLD of both lungs and whole lungs),imaging data of chest(High-resolution computed tomography(HRCT)of chest that before and 4?24 months after radiotherapy),mode of radiotherapy and prescription dose.After radiotherapy,HRCT of chest,was used to evaluate RIPF according to CTCAE-V4.0 criteria.44 patients who received radiotherapy after modified radical mastectomy of left breast cancer were divided into two groups:RIPF group and no RIPF group.The above clinical factors and dosimetry factors were analyzed by SPSS.25 software.Results:The CT imaging results of the patients suggested that 14 patients(32%)had no RIPF,30 patients(68%)had grade 1 or 2 RIPF,and there was no grade 3 or higher.The median time for the occurrence of RIPF is 8 months after radiotherapy,and the time range of RIPF from 4 months to 15 months after radiotherapy.Univariate analysis showed that there were significant differences in left lung V5,V20,V25,V30,V35,MLD,right lung V5,V10,MLD and whole lung Vs,V10,V20,V25,V30,MLD.The group with pulmonary fibrosis was higher than that without pulmonary fibrosis,but there was no significant difference in other clinical factors and the dosimetric parameters.Multivariate regression analysis of the dosimetric parameters showed that left lung V30 and V35 were independent risk factors for RIPF,with V30<18%and V35<15%as demarcation points.the sensitivity scores of V30?V35 for the prediction of RIPF were 86.7%and 86.7%,and the specificity scores were 85.7%and 85.7%;respectively.Conclusion:Different dose volumes of ipsilateral lung and MLD are related to RIPF after VMAT that followed with modified radical mastectomy of left breast cancer.In addition,the lung volume at low dose has the same effect on the occurrence of radioactive pulmonary fibrosis as that at high dose,may all have some effect.In the radiotherapy of breast cancer,in addition to the classical predictors of radiation-induced lung injury,such as V20 and V30,the control of V5 and V10 should be further strengthened to reduce the impact of side effect of radiotherapy on patients' long-term life after radiotherapy.