Discussion On The Relationship Between Lower Level Of Ps-Tg And The Ratio Of Ps-Tg To TSH And Response To ¹³¹I Therapy In Thyroid Papillary Carcinoma

ObjectiveTo discuss the clinical outcome of ¹³¹I therapy in papillary thyroid cancer with pre-ablative stimulated thyroglobulin?ps-Tg?below 10 ng/ml and evaluate the predictive value of lower level ps-Tg and ps-Tg/TSH ratio for the excellent clinical outcome of ¹³¹I therapy with PTC.To analysis the clinical prognosis of PTC patients with different recurrence risk and try to utilize the above critical value to evaluate their disease-free status.To investigate the effect of negative thyroglobulin antibody?<115IU/ml?on the clinical outcome of PTC patients after ¹³¹I therapy.MethodsCollect the data of all PTC patients hospitalized in our department from October 2015to October 2018,perform ¹³¹ I therapy for the first time after operation,Select 126 PTC patients with ps-Tg<10ng/ml and Tg Ab<115IU/ml,and then follow-up regularly.According to the new response to therapy assessment system in the 2015 ATA guidelines,response to initial ¹³¹I therapy was divided into four groups[excellent response?ER?,indeterminate response?IDR?,biochemical incomplete response?BIR?and structural incomplete response?SIR?],and BIR,SIR were further classified as incomplete response?IR?.The general clinicopathological characteristics,ps-Tg level,ps-Tg/TSH ratio and lymph node metastasis of three groups were compared;then IDR and IR was combined into non excellent response?non-ER?,and the ps-Tg level and ps-Tg/TSH ratio of the ER and non ER groups were compared.Then the diagnostic critical point?DCP?of ps-Tg and ps-Tg/TSH ratio was obtained to evaluate the predictive value of ps-Tg and ps-Tg/TSH ratio for disease-free survival after ¹³¹I therapy.According to the recurrence risk stratification system in the 2018 thyroid cancer diagnosis and treatment specification,126 PTC patients were again divided into three groups:low-risk group,medium-risk group and high-risk group.We analyzed the clinical outcome of patients with different recurrence risk and tried to use ps-Tg level and ps-Tg/TSH ratio threshold predicting disease-free survival after ¹³¹I therapy to evaluate its excellent clinical outcome.Regard 33 IU/ml as the critical point of negative Tg Ab,126 PTC patients were classified into two groups:S1 group??33IU/ml?and S2 group?33IU/ml<S2<115IU/ml?.Then the satisfaction rate of clinical outcome between two groups was compared.ResultThere was no significant difference in age?F=0.655,P=0.521?,gender??²=1.730,P=0.421?,number of lesions??²=2.398,P=0.335?,neck ultrasound??²=3.310,P=0.156?,T stage??²=4.358,P=0.072?,distance from surgery??²=0.381,P=0.868?,tumor diameter?F=1.276,P=0.283?,TSH level?H=1.124,P=0.570?,follow-up time?H=0.891,P=0.640?,the scope of lymph node dissection??²=1.832,P=0.814?,lymph node?F=2.787,P=0.248?and the rate of lymph node metastasis?F=2.349,P=0.100?among the three groups;but there was significant difference in ps-Tg level and ps-Tg/TSH ratio?H=33.323,P<0.001 and H=32.564,P<0.001,respectively?among them.Two comparisons further made between groups in ps-Tg level and ps-Tg/TSH ratio,there was significant difference between ER and IDR?H=-41.093,adjusted P<0.001 and H=-41.090,adjusted P<0.001?,IR?H=-63.155,adjusted P<0.001 and H=-61.280,adjusted P=0.001?,but not between IDR and IR?H=-22.062,adjusted P=0.673and H=-20.190,adjusted P=0.799?.Also,there was significant difference in ps-Tg level,ps-Tg/TSH ratio between ER and non-ER?U=364.50,P<0.001 and U=372.00,P<0.001,respectively?.Area under ROC curve was 0.860?95%CI:0.793-0.926?,0.857?95%CI:0.793-0.921?respectively.And DCP was 2.15 ng/ml,0.044,respectively,with the maximum value of Jordan index 0.603,0.653,respectively;the accuracy 73.80%,80.95%,respectively;the sensitivity 92.30%,92.30%respectively;the specificity 69.00%,78.00%,respectively;the positive predictive value 43.60%,52.17%,respectively;the negative predictive value 97.20%,97.50%.There was no significant difference in the level of ps-Tg between different risk stratification groups?H=2.297,P=0.317?,but the difference between the risk stratification of recurrence and the response to ¹³¹I treatment was statistically significant??²=13.937,P=0.004?.Among the 126 patients with PTC,70 were at low risk,including 60 cases of ER,8 of IDR and 2 of IR;48 were at medium risk,including 38 cases of ER,8 of IDR and 2 of IR;8 were high risk,including 2 cases of ER,5 of IDR and 1 of IR.Take 2.15ng/ml as the cut-off value of ps-Tg and 0.044 the cut-off value of ps-Tg/TSH ratio to evaluate disease-free survival status among three risk stratification of recurrence,With accuracy 50.0%,77.1%,75.0%,77.1%,77.1%,87.5%,respectively;sensitivity 30.0%,100.0%,66.7%,90.0%,90.0%,100.0%,respectively;specificity 53.0%,71.1%,100.0%,66.7%,26.3%,50.0%,respectively;positive predictive value 53.0%71.1%,100.0%,66.7%,26.3%,50.0%,respectively;negative predictive value 82.0%,100.0%,50.0%,97.8%,96.6%,100.0%,respectively.There was no significant difference in Tg Ab level among the three groups?P>0.05?.But there was significant difference in the clinical efficacy satisfaction rate between the two groups??²=25.727,P<0.001?,with the clinical outcome satisfaction rate of S1?88.20%?significantly higher than that of S2?41.70%?.ConclusionBoth ps-Tg and ps-Tg/TSH ratio have a definite predictive value for clinical outcome after ¹³¹I treatment in the PTC patients whose ps-Tg<10 ng/ml,and ps-Tg/TSH ratio has a better predictive value;The lower the risk stratification of postoperative recurrence,the better the efficacy of ¹³¹I treatment;And it may be more valuable to evaluate the excellent clinical outcome of PTC patients with different recurrence risk using ps-Tg/TSH ratio to predict the disease-free survival threshold after ¹³¹I therapy;For the postoperative PTC whose Tg Ab<115 IU/ml,the lower Tg Ab level,the better effect of¹³¹I therapy.