The application value of 18F-FDG PET/CT in patients with differentiated thyroid cancer of high thyroglobulin level and negative 131I whole body scan

Abstract

Objective To estimate the valuate of 18F-FDG PET/CT as a routine examination for the patients with suspected differentiated thyroid carcinoma (DTC) recurrence, accompanied by the increase of thyroglobulin (Tg) and negative 131I whole body scan. Method 32 patients who suffered from DTC receiving post-operative 131I therapy, with increase of Tg and negative 131I whole body scan, were performed 18F-FDG PET/CT, and follow-up continued. Patients were divided into two groups according to the level of Tg: H group (Tg>10 ng/ml) and L group (Tg<10 ng/ml) . Histopathological examination, ultrasound examination and clinical follow-up were used to verify the result, and assess the clinical value of PET/CT. Result PET/CT imaging results indicated that among 32 patients, there were 20 positive (18 true-positive and 2 false-positive) and 12 negative (4 true-negative and 8 false-negative) . Among 18 patients with true positive, 15 cases with local disease, 6 cases with distant metastasis, and 3 patients with both local invasion and distant metastasis. The overall sensitivity, specificity and accuracy were 69.2%, 66.7% and 68.8%, respectively. Compared with the L group, H group developed higher sensitivity (80% versus 33.3%) , specificity (100% versus 60%) and accuracy (80.9% versus 45.5%) . In 32 patients, 18 cases (56.2%) changed the strategies of clinical treatment, and 12 cases (37.5%) were received the radical operation under guidance. Conclusion 18F-FDG PET/CT can detect and locate accurately for the regional metastasis and recurrence of patients with DTC, accompanied by the increase of serum Tg and negative 131I whole body scan. Therefore, it can be recommended as a routine diagnostic tool. Key words: Fluorodeoxyglucose F18; Positron-emission tomography; Tomography, X-ray computed; Thyroid neoplasms; Thyroglobulin; Serum albumin, radio-iodinated