Diagnostic Value Of Serum Anti-thyroglobulin Antibodies And Thyroglobulin MRNA Of Peripheral Blood In Patients With Differentiated Thyroid Carcinoma, Redifferentiation Therapy With Retinoic Acid In Differentiated Thyroid Carcinoma

Objective:1. To evaluate the diagnostic value of serum anti-thyroglobulin antibodies (TGAb) in thyroglobulin (TG)-negative and TGAb-positive (TG TGAb⁺) patients with differentiated thyroid carcinoma (DTC) after thyroid remnant ablation and ascertain the cut-off value of TGAb to differentiate between the recurrent/metastasized and disease-free patients.2. To detect the level of TG mRNA in peripheral blood samples of patients with DTC after thyroid remnant ablation by reverse transcription-polymerase chain reaction (RT-PCR) and to evaluate the diagnostic value of TG mRNA in DTC patients.3. To evaluate the effectiveness of retinoid acid (RA) for improving ¹³¹I uptake in recurrent/metastasized DTC with diagnostic ¹³¹I whole body scan (dWBS)-negative and TG-positive (dWBS^-TG⁺) and therapeutic effects in ¹³¹I-treated DTC patients with dWBS^-TG⁺ after RA induction.Methods:1. The clinical datas of the patients (n=169) histologically confirmed DTC were collected in Nuclear Medicine Department of West China Hospital of Sichuan University from January 2001 to September 2006. All patients underwent remnant ablation and showed TG-negative and TGAb-positive (TG^-TGAb⁺) by means of electrochemiluminescence immunoassay (ECLIA, Roche Company) (A measurable range of serum TG is 0.100-1000μg/L, TGAb is 10-4000 IU/ml. A serum TG level of below 1μg/L with suppressed TSH levels or 2μg/L with stimulated TSH levels was considered TG-negative. We defined TGAb-negative as under 10 IU/ml.) According to "the reference criteria", the patients were divided into recurrence/metastases group (n=59) and no evidence of disease (NED) group (n=110). The receiver operating characteristic (ROC) curve was performed by the nonparametric method. The cut-off value was defined as the threshold value of the maximum Youden Index (YI, YI= sensitivity + specificity-1). The symmetric measures of the two diagnostic methods (the reference criteria and the diagnostic standard as serum TGAb level alone) were analyzed using McNemar test and measure of agreement Kappa. And, the analysis of positive likelihood ratio (+LR) with different threshold values were carried out in the study.2. TG mRNA was detected by RT-PCR (Reverse transcription-polymerase chain reaction) in peripheral blood samples of the patients (n=162) with histologically confirmed DTC who were admitted to the Nuclear Medicine Department of West China Hospital of Sichuan University from April 2006 to February 2007. All patients underwent total or subtotal thyroidectomy, followed by radioiodine remnant ablation completely and thyroid hormone suppression of TSH. According to "the reference criteria" and the levels of serum TG/TGAb, the patients were divided into three groups:â‘ TG TGAb⁺ and recurrence/metastases (n=52); (2)TG⁺ TGAb^-and recurrence/metastases (n=60);â‘¢TGTGAband disease-free (n=50). We compared their accuracy (sensitivity and specificity) with serum TG and TG mRNA in peripheral blood in monitoring recurrence/metastases of the DTC patients. The correlated analyses between positive rate of TG mRNA in peripheral blood and the clinical characteristic of DTC patients (TNM stage, age, sex, histological type and location of metastases) were carried out using nonparametric Spearman correlation coefficient methods.3. The patients (n=20) of dWBS^-TG⁺ with DTC were given RA at 1.0mg/kg/d for 8 weeks, followed by ¹³¹I treatment. The changes of ¹³¹I uptake and serum TG levels were measured and compared in the patients before and after RA induction therapy. The clinical outcome was classified and evaluated according to the Response Evaluation Criteria in Solid Tumors (RECIST). The side-effects were documented according to the common toxicity criteria (CTC) of the European Organization for the Treatment of Cancer (EORTC).Results:1. Serum TGAb level (1368.24±1343.45)IU/ml of the patients of recurrence or metastases group was significantly higher than that (153.55±539.17)IU/ml of NED group (P=0.000). The area under the ROC curve was 0.945 and its asymptotic 95% confidence interval was (0.911, 0.978), that was high statistical significance. The cut-off value of TGAb was determined and interpreted at 204.00 IU/ml with sensitivity (91.50%) and specificity (89.10%). McNemar test showed that the diagnostic result of the two criterias (the reference criteria and the diagnostic standard as serum TGAb level alone) was not statistically significant (P=0.143). Measure of agreement Kappa was "0.785, P=0.000", that showed the agreement of the two diagnostic methods was high statistical significance. When the pre-test probability fixed and except for the mixed function of other factors, the possibility of recurrence or metastasis of TGAb≥204 IU/ml was 88.32 times that of TGAb＜204 IU/m; the possibility of recurrence or metastasis of TGAb＞1000 IU/ml was 1.12 times that of 204 IU/ml≤TGAb≤1000 IU/ml, 4.03 times that of 100 IU/ml≤TGAb＜204 IU/ml, 24.79 times that of 10 IU/ml≤TGAb＜l00 IU/ml; the possibility of recurrence or metastasis as 204 IU/ml≤TGAb≤1000 IU/ml was 3.59 times that of 100 IU/ml≤TGAb＜204 IU/ml, 22.10 times that of 10 IU/ml≤TGAb＜l00 IU/ml; the possibility of recurrence or metastasis as 100 IU/ml≤TGAb＜204 IU/ml was 6.15 times that of 10 IU/ml≤TGAb＜100 IU/ml.2. The TG mRNA assay had greater sensitivity than the serum TG measurement (86.61% vs. 53.57%; P＜0.001) with the routine clinical examinations as the "reference standard" for the identification of recurrence/metastases. There was not statistically significant difference in comparison with the specificity of TG mRNA assay and serum TG measurement (94.00%, 100%, respectively; P＞0.05). In TGAb-positive patients (n = 52) with DTC, the sensitivity of TG mRNA (86.54%) was significantly higher than that of serum TG (0%) to identify recurrent/metastatic thyroid disease (P＜0.001). In TGAb-negative patients (n = 110) with DTC, the sensitivity of serum TG (100%) was higher than that of TG mRNA (86.67%). There was a significantly positive correlation between positive rate of TG mRNA in peripheral blood and TNM stages of DTC patients (Spearman correlation coefficient is 0.560, P = 0.000＜0.001). Positive rate of TG mRNA in peripheral blood did not correlate with ages, sex, pathological types and location of metastases, respectively (P＞0.05).3. Therapy was well tolerated except one patient who had to be disrupted after taking RA 15 days because of significant cheilitis, mucositis, conjunctivitis, pruritus. Radioiodine uptake of recurrence/metastases markedly increased in 6 patients (31.57%), mildly increased in 5 patients (26.32%), and unchanged in 8 patients (42.11%). Serum TG levels increased in 11 patients (57.89%), unchanged in 7 patients (36.84%), and decreased in 1 patient (5.26%) after RA induction. Serum TG levels increased in 1 patient (5.26%), unchanged in 6 patients (31.58%), and decreased in 12 patients (63.16%) after ¹³¹I treatment. There were 11 responders (57.89%) and 8 non-responders (42.11%) after RA induction. The complete responder (CR) was 0%, incomplete responder (ER.) was 94.74% (18/19), and progressive disease (PD) was 5.26% (1/19). Radioiodine uptake did not correlate with serum TG levels (Spearman correlation coefficient is 0.415, P = 0.077＞0.05). There was not significant correlation between ¹³¹I uptake and success/failure of ¹³¹I treatment, between serum TG levels of RA induction and success/failure of ¹³¹I treatment, respectively (Spearman correlation coefficient is 0.253, 0.247, respectively; P value is 0.297, 0.308, respectively, both of them are more than 0.05). There was significantly positive correlation between tWBS and success/failure of ¹³¹I treatment (Spearman correlation coefficient =0.687＞0.5, P = 0.004＜0.05). The side effects including mucositis, cheilitis, desquamation, hair loss, pruritus, conjunctivitis and raised transaminases occurred in most patients.Conclusion:1. Serum TGAb is a marker for recurrence or metastasis in TG-negative and TGAb-positive DTC patients undergone thyroidectomy and ¹³¹I ablation therapy. The OOP of TGAb level is 204 IU/ml, that is to say, serum TGAb level upon 204 IU/ml may be associated with the persistence or recurrence of DTC. The higher serum TGAb level, the more possible recurrence or metastasis is.2. Circulating TG mRNA is a more sensitive marker to identify recurrent/metastatic DTC than serum TG, particularly in patients with TGAb-positive. The higher clinical stages of DTC, the higher positive rate of TG mRNA is. The positive expression of TG mRNA indicates the poor prognosis and should be treated actively.3. RA induction can increase ¹³¹I uptake in some recurrence/metastases, thus it might be an option for advanced thyroid carcinoma and deserves further investigation.