Objective: The most important follow-up method for differentiated thyroid carcinoma patients is I-131 whole body scintigraphy (WBS). We retrospectively investigated findings of patients who were referred for WBS with incidentally performed concurrent (1-14 day interval) Tc-99m pertechnetate thyroid scintigraphy (TS) findings in order to compare two methods.

Materials and Methods: Thirty five patients (25 Female, 10 Male; 19-67 years; mean age: 45 years) with diagnosis of differentiated thyroid carcinoma were included into the study. Their thyroid hormone replacement were stopped and iodine free diet was applied 3 weeks prior to the WBS. Iodine-131 WBS of 35 patients and concurrent TS of 12 patients were evaluated.

Results: Pathological diagnoses of patients were: papillary (n=29), follicular (n=3), medullary and papillary (n=2) and follicular variant of papillary carcinoma (n=1). The thyroid stimulating hormone (TSH) levels prior to the WBS were 31-143mIU/L (mean: 60 mIU/L) and thyroglobulin (TG) levels were 0.2-102 ng/mL (mean: 14 mIU/L). Results of 9 out of 12 patients who were evaluated with both WBS and TS were in agreement. One patient had one more focus of residual tissue at WBS which was not seen on TS and 2 patients had residue tissue on WBS but there was no activity on their TS. Additionally 6 patients out of 35 patients had extrathyroidal involvement on WBS.

Conclusion: Although statistical analysis couldn't be performed because of inadequate number of subjects, WBS was found to be superior to TS for showing residual tissue. Additionally in terms of opportunity of scanning whole body, WBS has to be the preferred method to prefer in follow-up of differentiated thyroid cancer patients.