| Objective:This study aims to analyze the incidence of hypothyroidism after radiotherapy for breast cancer,and analyze the correlation with thyroid dose parameters,so as to provide a basis for thyroid dose limitation in breast cancer patients undergoing adjuvant radiotherapy,and provide more comprehensive and professional guidance for the long-term management of breast cancer patients.Methods:A total of 372 patients with stage I-III breast cancer who underwent radiotherapy in the Affiliated Tumor Hospital of Guizhou Medical University from July 2018 to July 2019 were enrolled in this study.According to the inclusion and exclusion criteria,a total of 120 female patients were included in this study.According to whether the target area of radiotherapy included supraclavicular lymph node drainage area,the subjects were divided into A and B groups : group A was simple breast /chest wall radiotherapy(n = 60),group B was breast / chest wall + supraclavicular area(n = 60).Thyroid function(T3,T4,FT3,FT4,TSH)and thyroid ultrasound were detected before radiotherapy,1 month,6 months,12 months,18 months,24 months and 36 months after radiotherapy,and relevant clinical symptoms were collected.The relationship between thyroid volume and mean dose(Dmean)of thyroid(including left lobe and right lobe of thyroid),percentage of thyroid volume received 5 Gy,10 Gy,20 Gy,30 Gy,40 Gy and 50 Gy(V5-V50),thyroid volume(i ncluding left lobe and right lobe of thyroid),other clinical factors and hypothyroidism(HT)were analyzed.According to the results of thyroid function,the patients were divided into hypothyroidism group and normal group.The related data of the two groups were analyzed by single factor analysis(chi-square test,independent sample t test,and Mann-Whitney U test [ depending on the data type ])to assess the difference between groups.Binary logistic regression analysis was performed on the indicators with difference in single factor analysis to obtain the independent predictor of hypothyroidism,which was then taken into the receiver operating character(ROC)curve for analysis.Determine the predictive value of each index for hypothyroidism.P < 0.05 indicated that the difference was statistically significant.Results:Among 120 patients,20 cases(16.67 %)had hypothyroidism(5 cases of clinical hypothyroidism,15 cases of subclinical hypothyroidism).Among them,there were 2 cases of hypothyroidism in group A(0.02 %)and 18 cases in group B(15 %),and the difference in the incidence of hypothyroidism between the two groups was statistically significant(P < 0.001).The levels of FT3 and F4 in group B were significantly different from those in group A at 36 months after radiotherapy,and the TSH level was significantly different at 18,24 and 36 months after radiotherapy(P <0.05).The differences in V20,V30,Dmean and Dmean of the left lobe between HT group and normal thyroid function group in group B were statistically significant(P values were 0.011,0.001,< 0.001,0.033,respectively).Thyroid V30(P = 0.045 OR= 1.006 95 % CI = 0.906-1.128)and Dmean(P = 0.01,OR = 1.009,95 % CI =1.002-1.017)were independent prognostic factors for HT after supraclavicular field radiotherapy in breast cancer.According to ROC curve,thyroid V30 > 52 % and Dmean > 33.9 Gy have clinical reference value for HT prediction,and the average thyroid dose Dmean model is superior to V30.Conclusions:1.The incidence of hypothyroidism(including clinical hypothyroidism and subclinical hypothyroidism)after supraclavicular radiotherapy for breast cancer was15 %.2.The occurrence of hypothyroidism after radiotherapy is correlated with V20,V30,Dmean and Dmean in the left lobe of the thyroid,The higher the V20,V30,Dmean and Dmean in the left lobe of the thyroid are,the greater the risk of HT is.3Thyroid V30 and Dmean have good predictive value for hypothyroidism after radiotherapy.When V30 > 52 % and Dmean > 33.9 Gy,they have clinical reference value for HT,and the average thyroid dose Dmean model is better than V30. |
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