Aim: Assessment of the clinical impact of a positron emission tomography/computed tomography (PET/CT) with FDG in the management of differentiated thyroid cancer (DTC) in patients with increased or positive thyroglobulin autoantibodies (AbTg).
Methodology: Retrospective study involving 15 patients seen in the follow-up with confirmed DTC primarily treated with total thyroidectomy and Iodine 131. Patients presenting with increased AbTg and a negative or non informative conventional evaluation were included. Inclusion was independent of presence or not of metastatic lymph nodes at time of diagnosis. The results of the PET/CT were correlated with histology and/or clinical follow up. The clinical impact was determined on a change of intention to treat, which was decided upon in multidisciplinary meetings, based on the PET/CT result.
Results: We observed in 14 out of 15 eligible patients: 10 true positive examinations (confirmed by histology in 7 patients and clinical follow up in 3) 7 patients with cervical uptake, 1 cervical and mediastinal uptake, 1 cervical and lung uptake and 1 liver uptake, 4 true negative examinations with negative follow up of on the average 22 months (1836 months) and no false positive or false negative results. The intention to treat was modified in 73.3% (11/15 patients). The variation in the values of the AbTg of the true positive and the true negative group was similar and did not allow for a threshold value.
Conclusion: PET/CT with FDG seems to be very useful in the therapeutic management of recurrence of DTC in the case of increased or positive AbTg, in particular for the patients with N1 at the initial staging. Further studies are suggested to confirm the very promising negative predictive value and specificity of this study in a larger number of patients with longer follow up.