TITLE:
Can I-124 PET/CT Predict Pathological Uptake of Therapeutic Dosages of Radioiodine (I-131) in Differentiated Thyroid Carcinoma?
AUTHORS:
Gauke K. Lammers, Jan Paul Esser, Pieternel C. M. Pasker, Marina E. Sanson-van Praag, John M. H. de Klerk
KEYWORDS:
I-124, PET, I-131, Thyroid, Carcinoma
JOURNAL NAME:
Advances in Molecular Imaging,
Vol.4 No.3,
July
4,
2014
ABSTRACT: Introduction: The aim of the study was to assess the role of I-124
PET/CT in the prediction of uptake of a therapeutic dosage I-131 during
follow-up of patients with differentiated thyroid cancer (DTC). Methods: The
results of 34 I-124 PET/CT scans performed in our hospital between 2007 and
2012 were retrospectively evaluated. All scans were made in patients under
follow up, replacing the diagnostic I-131 or I-123 scintigraphy. In all cases
thyroglobulin (Tg) was stimulated (by recombinant thyroid stimulating hormone
(rhTSH) or thyroid hormone withdrawal). A dosage of 40 MBq I-124 was used, with
scans at 24 hours and 96 hours after administration. Results were compared to
subsequent I-131 post-treatment scans (6 cases) and a combination of follow up,
stimulated Tg and other imaging tools results available to assess presence of
recurrence. Results: Recurrence of DTC was found in 14/34 cases. I-124 PET/CT
correctly detected recurrence in 2 cases, with false negative results in 12
cases. In 1 case a false positive I-124 PET/CT result was recorded. 19 true
negative results were found. For I-124 PET/CT this meant a sensitivity of 14%
and a specificity of 95%. Positive predictive value was 67%, negative
predictive value 61%. Post-treatment I-131 uptake (6 cases) was correctly
predicted in 1 case, with false negative results in 4 cases and 1 true negative
result. Conclusions: In this study I-124 PET/CT did not reliably detect
recurrent differentiated thyroid carcinoma. More importantly it failed to
predict I-131 uptake on post-treatment scintigraphy in a significant number of
cases, which would lead to under-treatment.