OBJECTIVE: To evaluate the clinical benefit of pre-ablation scanning in patients with differentiated thyroid carcinoma. MATERIALS AND METHODS: We assessed scannings and serum thyroglobulin (Tg) measurements before the first ablative therapy in 100 patients with hypothyroidism submitted to total thyroidectomy. Scanning was considered clinically significant when it showed resectable metastases or which were treated with higher doses than the initially proposed one (100 mCi of 131I), in addition to cases with no uptake and Tg levels < 5 ng/ml not requiring radioiodine therapy. RESULTS: Scanning showed uptake corresponding to lymph node metastases in 10 patients (10%), distant metastases in 5 (5%), uptake only in the thyroid bed in 76 (76%), and was negative in 9 (9%). The procedure was considered clinically relevant in 18% of the patients (indicating the need of surgery, dose increase or discontinuation of radioiodine therapy). In patients with Tg > 10 ng/ml, scanning influenced therapeutic management in 41% of the cases due to detection of metastases, while in patients with Tg < 10 ng/ml scanning influenced therapeutic management in only 10% of the patients, most of which did not receive radioiodine therapy. CONCLUSION: Scanning provides clinically significant data (presence of metastases) in many patients with Tg levels > 10 ng/ml and, therefore, should be used in these cases.

Keywords: Thyroid cancer, Scanning, Ablative therapy