Comparison of serum thyroglobulin, 131I and 201Tl scintigraphy in the postoperative follow-up of differentiated thyroid cancer.

To evaluate the significance of 201Tl scintigraphy, 131I scintigraphy and serum thyroglobulin (Tg) levels in the postoperative follow-up of differentiated thyroid carcinoma, 86 patients were examined. Serum Tg was found to have the highest sensitivity (97%) as well as specificity (100%) for the detection of local tumour or metastases. Sensitivity and specificity of 131I scintigraphy after a therapeutic dose of 6100 MBq were 77 and 98%, respectively. For a diagnostic dose of 185 MBq 131I, sensitivity and specificity were 57 and 98%; for 74 MBq 201Tl these figures were 55 and 91%, respectively. The combination of serum Tg and 131I had a sensitivity of 100% and a specificity of 98% to detect the presence, although not always the localization, of persistent or recurrent tumour. 201Tl scintigraphy can provide useful additional information about the localization of local recurrences and metastases, especially in cases where serum Tg becomes positive and 131I uptake is absent. One has to bear in mind the possibility of discrepant results of 131I and 201Tl scintigraphy, in different tumour sites in one patient. There appeared to be no specific tendency for differential uptake of 131I versus 201Tl in relation to tumour type (papillary versus follicular) or localization with the possible exception of a higher preference for 131I uptake in cases of micrometastases of papillary cancer in the lungs.