Endocrine Abstracts (2017) 49 EP1410 | DOI: 10.1530/endoabs.49.EP1410

The impact of post-radioiodine therapy SPECT/CT on risk stratification in differentiated thyroid cancer; a bi-institutional study

Szabina Szujo1, Livia Sira2, Laszlo Bajnok1, Beata Bodis1, Ferenc Gyory5, Orsolya Nemes1, Karoly Rucz1, Peter Kenyeres1, Zsuzsanna Valkusz6, Krisztian Sepp6, Erzsebet Schmidt3, Zsuzsanna Szabo3, Sarolta Szekeres3, Katalin Zambo3, Sandor Barna4, Endre V Nagy2 & Emese Mezosi1

1Ist Department of Medicine, University of Pecs, Pecs, Hungary; 2Department of Medicine, Faculty of Medicine, University of Debrecen, Debrecen, Hungary; 3Department of Nuclear Medicine, University of Pecs, Pecs, Hungary; 4Department of Nuclear Medicine, Faculty of Medicine, University of Debrecen, Debrecen, Hungary; 5Department of Surgery, Faculty of Medicine, University of Debrecen, Debrecen, Hungary; 6Ist Department of Medicine, University of Szeged, Szeged, Hungary.

Objective: SPECT/CT has numerous advantages over planar and traditional SPECT images. The aim of this study was to evaluate the role of post-radioiodine therapy SPECT/CT of patients with differentiated thyroid cancer (DTC) in early risk classification and in prediction of late prognosis.

Patients and Methods: 323 consecutive patients, 181 at the University of Pecs and 142 at the University of Debrecen, were investigated after their first radioiodine treatment (1100–3700 MBq). Both SPECT/CT and planar camera images of the head, neck, chest and abdomen regions were taken four days after radioiodine therapy. Patients were re-evaluated 9–12 months later as well as at the end of follow-up (median 37 months).

Results: Post-radioiodine therapy SPECT/CT showed metastases in 22% of patients. Lymph node, lung and bone metastases were detected in 61, 13 and 5 patients, respectively, resulting in early reclassification of 115 cases (36%). No evidence of disease was found in 251 cases at 9-12 months after radioiodine treatment and 269 patients at the end of follow-up. To predict residual disease at the end of follow-up, the sensitivities, specificities and diagnostic accuracies of the current risk classification systems and SPECT/CT were: ATA: 77%, 47% and 53%; ETA: 70, 62 and 64%; SPECT/CT: 61, 88 and 83%, respectively. There was no difference between cohorts of the two institutions when data were analyzed separately.

Conclusions: Based on our bi-institutional experience, the accuracy of post-radioiodine SPECT/CT outweighs that of the currently used ATA and ETA risk classification systems in the prediction of long-term outcome of DTC.