Objective: The use of 201Tl scintigraphy as a routine imaging modality in the follow-up of patients with differentiated thyroid carcinoma (DTC) is controversial. The purpose of this retrospective study was to evaluate the diagnostic accuracy and clinical impact of routine 201Tl scintigraphy in the follow-up of patients with DTC.
Materials and methods: Three hundred and twenty-one patients (261 women, 60 men) with DTC (243 papillary thyroid carcinomas, 78 follicular thyroid carcinomas) were enrolled in this study. Two hundred and seventy-six patients underwent total or near total thyroidectomy (group 1) and 45 patients underwent subtotal thyroidectomy or unilateral lobectomy (group 2). A total of 1523 201Tl scintigraphy examinations were performed between 1987 and 2003. The duration of follow-up ranged from 13 to 204 months. 201Tl scintigraphy was performed 10 and 60 min after intravenous administration of 74 MBq 201Tl chloride.
Results: In group 1, 55 recurrent lesions were confirmed in 39 patients. In a patient-based analysis, the sensitivity, specificity, positive and negative predictive values, and accuracy of 201Tl scintigraphy for detecting recurrent DTC were 71.8%, 98.3%, 87.5%, 95.5% and 94.6%, respectively. In a lesion-based analysis, the sensitivity, specificity, positive and negative predictive values, and accuracy of 201Tl scintigraphy were 63.6%, 99.7%, 89.7%, 98.5% and 98.3%, respectively. Of the 35 thallium-positive recurrent lesions, 21 (60%) were removed by surgery and seven (20%) were treated with external-beam radiation therapy. All the thallium-negative recurrent lesions were treated with 131I therapy. The difference between the management of thallium-positive and thallium-negative recurrences was statistically significant (P<0.001). In group 2, 10 recurrent lesions were confirmed in seven patients. In a patient-based analysis, the sensitivity, specificity, positive and negative predictive values, and accuracy of 201Tl scintigraphy for detecting recurrent DTC were 85.7%, 94.7%, 75%, 97.3% and 93.3%, respectively. In a lesion-based analysis, the sensitivity, specificity, positive and negative predictive values, and accuracy of 201Tl scintigraphy was 80%, 97.5%, 80%, 97.5% and 95.6%, respectively. All of the seven patients were treated with completion of total thyroidectomy and subsequent 131I ablation therapy.
Conclusions: 201Tl scintigraphy was not a highly sensitive imaging modality in routine follow-up of patients with DTC after total thyroidectomy. However, it had a clinical impact on the choice of optimal therapeutic approaches. In the follow-up of patients who underwent partial thyroidectomy, 201Tl scintigraphy was useful in the detection of recurrent DTC.