Association Between Sternal Dosimetric,Clinical Parameter And Hematological Toxicity Of Adjuvant Radiotherapy After Modified Radical Mastectomy For Breast Cancer

Objective:To research the association between sternal dosimetry parameters,clinical parameters and hematological toxicity of adjuvant radiotherapy after modified radical mastectomy for breast cancer.Methods:We retrospectively analyzed clinical data and radiotherapy data of 60 patients treated with radiotherapy after modified radical mastectomy in the Hebei General Hospital from Dec.2015 to May 2019.V_5,V_10,V_20,V_30,V₄₀,D_mean,D_max,D₂₀,D₄₀,D₆₀,D₈₀of the sternum were recorded on DVH diagram.Collecting and sorting of patients with clinical parameters:age,height,body weight,body surface area,body mass index,number of lymph node dissection,number of lymph node metastasis,chemotherapy and radiotherapy interval,blood baseline value（the number of blood cellsbefore radiotherapy）and sternum volume,thoracic transverse diameter,thoracic vertical diameter,thoracic ratio total of 13indexes.The hematological indexes before and during radiotherapy were recorded,hematological toxicity was graded.Binary Logistic regression was used to examine the relationship between dosimetry parameters,clinical parameters and hematologic toxicity.The Receiver Operating Characteristic（ROC）curve is used to evaluate the threshold values of dosimetric parameters to avoid hematological toxicityResults:1.Relationship between sternal dosimetry parameters and hematological toxicity:1.1 Sternum V₂₀,V₃₀,V₄₀were the factors affecting occurrence of≥2grade HT,V₃₀is an independent risk factor（P=0.031）;sternum V₁₀,V₂₀,V₃₀,V₄₀,D₆₀,D₈₀were the factors affecting occurrence of≥2 grade leukopenia,V₄₀were independent risk factors（P=0.014）;Sternum V₅and V₁₀were the factors affecting occurrence of≥3 lymphocytopenia,no independent influencing factors were found.The cut-off point of V₃₀was24.38cm³,and the cut-off point of V₄₀was 6.48cm³.When sternal V₃₀≥24.38cm³,the incidence of≥grade 2 HT increased significantly（52%,8%P=0.001）;when sternal V₄₀≥6.48cm³,the incidence of≥2 grade leukopenia increased significantly（61%,32%P=0.035）.1.2 There was a negative correlation between sternal V₂₀,V₃₀,V₄₀and leucocyte nadir.V_20,V₃₀was negatively correlated with neutrophils nadir.V₅,V₁₀,V₂₀,V₃₀were negatively correlated with lymphocytes nadir.2.Relationship between clinical parameters and hematological toxicity:2.1 The baseline WBC（P=0.048）and lymphocyte values（P=0.048）.were independent risk factors for grade 2 and above leucopenia and grade 3and above lymphocytopenia,respectively.2.2 Further studies on factors influencing sternal dose showed that thoracic ratio and BMI were negatively correlated with sternal V₄₀.Conclusion:1.For patients receiving adjuvant radiotherapy after modified radical resection of breast cancer,reducing sternal V₃₀can reduce the occurrence of acute hematological toxicity of grade 2 or above.Reducing sternum V₄₀can reduce the occurrence of grade 2 and above leukopenia.2.The lower the baseline value of leucocyte,the more prone to≥grade2 leucocyte toxicity.The lower the baseline value of lymphocytes,the more likely the occurrence of≥grade 3 lymphotoxicity.