A Kukulska1, J Krajewska2, Z Kołosza3, E Paliczka-Cies Lik2, Z Puch2, E Gubała2, A Król2, M Kalemba2, A Kropin Ska2, B Jarząb2. 1. Nuclear Medicine and Endocrine Oncology Department akukulska@io.gliwice.pl. 2. Nuclear Medicine and Endocrine Oncology Department. 3. Department of Epidemiology and Silesia Cancer RegistryM.Sklodowska-Curie Memorial Cancer Center and Institute of Oncology, Gliwice Branch, Gliwice, Poland.
Abstract
INTRODUCTION: Available methods, including serum thyroglobulin (Tg) measurement and whole-body scan (WBS) performed after radioiodine administration, allow for a precise diagnostics in differentiated thyroid cancer (DTC). However, some asymptomatic patients demonstrate negative WBS despite a high Tg serum concentration. In these subjects, fluorodeoxyglucose-positron emission tomography (FDG-PET) should be considered. The primary aim of our study was to evaluate a diagnostic value of FDG-PET in asymptomatic hyperthyroglobulinemia. The secondary one was to determine a prognostic value of a negative FDG-PET result in DTC patients with elevated Tg level. MATERIAL: One hundred and ten FDG-PET/CT scans were retrospectively analyzed, 85 scans were done under TSH stimulation and 25 on LT4 suppressive therapy. Follow-up ranged between 4 and 9 years. RESULTS: The first FDG-PET/CT detected cancer foci in 49 subjects with a global sensitivity of 45%. When the sensitivity was evaluated with reference to TSH stimulation and suppression, its values were 50 and 28% respectively. In 42 patients, FDG-PET failed to diagnose the reason for elevated Tg level. During further follow-up, in 17 of them, DTC recurrence was detected by other methods (CT, MRI, US). Fourteen subjects with asymptomatic hyperthyroglobulinemia were free of DTC progression for at least 4 years. CONCLUSIONS: FDG-PET in DTC patients with asymptomatic hyperthyroglobulinemia constitutes a valuable diagnostic tool. Negative FDG-PET demonstrated a limited prognostic significance, as only every third patient did not show DTC progression. Moreover, negative FDG-PET does not justify less strict DTC monitoring, because it is related to 40% risk of relapse during the 5-year follow-up.
INTRODUCTION: Available methods, including serum thyroglobulin (Tg) measurement and whole-body scan (WBS) performed after radioiodine administration, allow for a precise diagnostics in differentiated thyroid cancer (DTC). However, some asymptomatic patients demonstrate negative WBS despite a high Tg serum concentration. In these subjects, fluorodeoxyglucose-positron emission tomography (FDG-PET) should be considered. The primary aim of our study was to evaluate a diagnostic value of FDG-PET in asymptomatic hyperthyroglobulinemia. The secondary one was to determine a prognostic value of a negative FDG-PET result in DTCpatients with elevated Tg level. MATERIAL: One hundred and ten FDG-PET/CT scans were retrospectively analyzed, 85 scans were done under TSH stimulation and 25 on LT4 suppressive therapy. Follow-up ranged between 4 and 9 years. RESULTS: The first FDG-PET/CT detected cancer foci in 49 subjects with a global sensitivity of 45%. When the sensitivity was evaluated with reference to TSH stimulation and suppression, its values were 50 and 28% respectively. In 42 patients, FDG-PET failed to diagnose the reason for elevated Tg level. During further follow-up, in 17 of them, DTC recurrence was detected by other methods (CT, MRI, US). Fourteen subjects with asymptomatic hyperthyroglobulinemia were free of DTC progression for at least 4 years. CONCLUSIONS:FDG-PET in DTCpatients with asymptomatic hyperthyroglobulinemia constitutes a valuable diagnostic tool. Negative FDG-PET demonstrated a limited prognostic significance, as only every third patient did not show DTC progression. Moreover, negative FDG-PET does not justify less strict DTC monitoring, because it is related to 40% risk of relapse during the 5-year follow-up.