Evaluation of radioiodine therapy in differentiated thyroid cancer subjects with elevated serum thyroglobulin and negative whole body scan using 131I with emphasize on the thallium scintigraphy in these subgroups.

OBJECTIVE Negative diagnostic 131I whole body scans with elevated serum thyroglobulin (Tg) levels are found in 20% of patients with differentiated thyroid cancer (DTC). Empirical radioiodine treatment has been advocated by some researchers, but has had with controversial outcomes. This anterospective study was performed to examine this dilemma and also to determine the capability of thallium (201TI) scintigraphy in these patients. MATERIALS AND METHODS A total of 21 patients who had a history of DTC and elevated serum Tg levels, together with a negative diagnostic 131I whole body scans (WBS), were included in the study. All patients underwent posttreatment 131I WBS. Patients with negative posttreatment 131I WBS then underwent 201TI scintigraphy. RESULTS The 21 included patients (9 women and 12 men) had a mean age of 53 +/- 14.17 years. The mean pretreatment and posttreatment Tg levels were 227.23 +/- 208.50 ng/ml and 163.43 +/- 282.57 ng/ml, respectively (p value <0.05). Eleven cases showed at least a 50% decrease in Tg value (remission group), 6 patients revealed less than a 50% decrease in Tg value (stable group), while 4 subjects demonstrated an increment in posttreatment Tg relative to pretreatment Tg value (progression group). The cumulative and last 131I doses in the remission, stable, and progression groups were not significantly different (p value >0.05). In the posttreatment 131I WBS, 10 patients showed abnormal findings in their images. In a follow-up scan after 201TI treatment, 7 out of 11 patients had positive scans. CONCLUSION The study indicates a positive effect of RAI therapy in DTC patients with elevated Tg and negative 131I WBS. In addition, 201TI scintigraphy can be useful as an alternative modality to improve tumoral detection in this situation and when access to a PET system is limited.