TECHNETIUM-99M-FURIFOSMIN IN THE FOLLOW-UP OF DIFFERENTIATED THYROID-CARCINOMA

Tumor scintigraphy with flow tracers, such as (TI)-T-201-chloride, has an established role in the follow-up of differentiated thyroid cancer . We investigated a new tracer, Tc-99m-furifosmin (Technescan Q12, Mal linckrodt Diagnostika, Hennef, Germany), in patients with elevated thy roglobulin levels or sonographic suspicion of lymph node metastases or recurrent disease. Methods: In a prospective study, we examined 20 pa tients with Tc-99m-furifosmin. All patients underwent a F-18-fluorodeo xyglucose (FDG) PET scan of the neck and chest. Positive 99mTc-furifos min findings were validated by biopsy, I-131 scan, CT or F-18-FDG PET examinations. Results: In three patients with cervical lymph node meta stases detected on a planar Tc-99m-furifosmin scan, we found a rapid t racer accumulation in the tumor (maximum < 2 min) and a significant wa shout in 2 of 3 patients after 4 hr. The visual contrast and the tumor -to-nontumor ratio was rather poor (average 1.2:1). In 3 additional pa tients, 3 pulmonary and 2 mediastinal lymph node metastases were detec ted by the Tc-99m-furifosmin SPECT scan. Two patients were true-negati ve, and in 13 of 18 patients, the tumor could be localized by F-18-FDG PET (10 cervical, 6 mediastinal, 4 pulmonary metastases, 1 bone metas tasis); 5 patients were false-negative. In 3 of these false-negative c ases we could not localize the tumor with other diagnostic methods. Tw o patients had a true-negative PET examination. Conclusion: The statis tical analysis of our data on Tc-99m-furifosmin reveals that the sensi tivity and 95% confidence interval of 33% (11%-56%) on a patient-by-pa tient basis and of 34% (17%-57%) for the lesion-by-lesion analysis is significantly lower than the sensitivity and 95% confidence interval o f 72% (50%-89%) on a patient-by-patient basis and of 91% (78%-100%) on lesion-by-lesion basis for F-18-FDG. The sensitivity of Tc-99m-furifo smin appears to be poor, even for cervical and mediastinal tumor manif estations where the value of (TI)-T-201-chloride is established.