Diagnostic Value Of ¹⁸F-FDG PET/CT In Suspected Recurrence Or Metastatic DTC Patients With Elevated Serum Tg Levels And Negative ¹³¹I-Dx-WBS

Differentiated thyroid cancer?DTC? is the most common thyroid cancer,It is a well-differentiated thyroid cancer, invasive weakly and progress slowly. The disease incidence of women were significantly higher than the men. Differentiated thyroid cancer including papillary thyroid cancer?PTC? and follicular thyroid cancer?FTC?. The treatment of patients with differentiated thyroid cancer has been widely recognized in the international community is total thyroidectomy or near total resection, ¹³¹ I ablation therapy and TSH suppression therapy. The main means of follow-up after treatment include ¹³¹I-whole body scan,serum thyroglobulin?Tg? and neck ultrasound?US? examination. The main purpose of the follow-up is to detect the DTC metastases or recurrent lesions and treatment early.About 10%-15% of DTC patients with elevated Tg levels and negative radioiodine diagnostic ¹³¹ I whole body scan(¹³¹I-Dx-WBS). The sensitivity and specificity of serum Tg in diagnosis of DTC were high. The elevated Tg levels prompt that the DTC patients with recurrence or metastasis. DTC patients with elevated Tg levels and negative ¹³¹I-Dx-WBS only indicates that they have recurrence or metastasis, but it can not provide accurate positioning information, whether to received empirical ¹³¹ I ablation therapy is controversial, but the best way for the treatment is to position diagnosis and underwent the surgical resection early. ¹⁸F-FDG PET/CT can detect the recurrence or metastasis DTC with elevated Tg levels and negative ¹³¹I-Dx-WBS, which can also be used to guide the follow-up treatment strategy. ObjectiveTo investigate the diagnostic value and the impact on treatment decision of ¹⁸F-FDG PET/CT in DTC patients with elevated Tg levels and negative ¹³¹IDx-WBS. Methods62 patients in our hospital underwent total thyroidectomy or subtotal resection, 60 patients were papillary thyroid cancer and 2 patients were follicular thyroid cancer confirmed by postoperative pathology. 1 to 3 months later, the patients received empirical ¹³¹ I ablation therapy?3.7 4.44 GBq?. After ¹³¹ I ablation therapy for 4 to 6 months, to underwent serum Tg, TGAb, neck US, ¹³¹I-Dx-WBS inspection after stopping the levothyroxine?LT4? for 20 days to a month. During the follow-up, the patients with positive serum Tg?Tg > 2?g/L? TGAb at normal levels and negative ¹³¹I-Dx-WBS had accepted ¹⁸F-FDG PET/CT. For the positive ¹⁸F-FDG PET/CT in DTC patients should underwent surgical excision or fine needle puncture cytology, the negative ¹⁸F-FDG PET/CT in DTC patients should underwent neck US examination, the positive neck US in patients should underwent surgical resection or fine needle puncture cytology. 49 cases of DTC patients were confirmed by biopsy pathology according to serum Tg levels in the stimulated state were divided into four groups 2 20?g/L, 20 50?g/L, 50 100?g/L, ? 100?g/L. To analyzed sensitivity and specificity of ¹⁸F-FDG PET/CT imaging in detection of DTC patients with recurrent or metastatic in each group. Results1.The sensitivity and specificity of ¹⁸F-FDG PET/CT in diagnosis of DTC with elevated Tg levels and negative ¹³¹I-Dx-WBS were 87.88%?29/33? and 75%?12/16?, respectively.2.When serum Tg in 2²0?g/L,the sensitivity and specificity of ¹⁸F-FDG PET/CT in diagnosis of DTC with elevated Tg levels and negative ¹³¹I-Dx-WBS were 66.67% and 60%.When serum Tg in 20⁵0?g/L,the sensitivity and specificity of ¹⁸F-FDG PET/CT in diagnosis of DTC with elevated Tg levels and negative ¹³¹I-Dx-WBS were 80% and 75%.When serum Tg in 50¹00?g/L,the sensitivity and specificity of ¹⁸F-FDG PET/CT in diagnosis of DTC with elevated Tg levels and negative ¹³¹I-Dx-WBS were 85.71% and 83.33%.When serum Tg in Tg ? 100?g/L,the sensitivity and specificity of ¹⁸F-FDG PET/CT in diagnosis of DTC with elevated Tg levels and negative ¹³¹I-Dx-WBS were 94.44% and 100%. The sensitivity and specificity of ¹⁸F-FDG PET/CT imaging in the diagnosis of DTC patients with recurrent or metastatic between the four groups was statistically significant difference?P < 0.05?.3.The results of ¹⁸F-FDG PET/CT changed the treatment strategy of 10?16.13%? patients, 10 patients underwent surgical resection. Conclusion1.The sensitivity and specificity of ¹⁸F-FDG PET/CT in diagnosis of DTC with elevated Tg levels and negative ¹³¹I-Dx-WBS were high. The sensitivity and specificity of ¹⁸F-FDG PET/CT were increasing with the serum Tg level gradually increased. ¹⁸F-FDG PET/CT in detection of the recurrence or metastasis DTC with elevated Tg levels and negative ¹³¹I-Dx-WBS has important significance.2.The results of ¹⁸F-FDG PET/CT changed the treatment strategy of 16.13% patients, ¹³¹I-Rx-WBS with ¹⁸F-FDG PET/CT complement each other, it had a certain value for the treatment decisions and efficacy assessment.