Cancer thyroïdien de souche folliculaire avec persistance d’anticorps antithyroglobuline : signification pronostique et apport de la TEP/TDM au F-FDG

Aim

To investigate the rate of persistence or/and recurrence of follicular cell-derived thyroid cancer with elevated serum antithyroglobulin antibody (TgAb) one year after ablative therapy. We also evaluated the predictive factors of persistence or/and recurrence and the clinical impact of PET/CT with FDG.

Methods

This retrospective study involved 154 TgAb+ patients. PET/CT was performed in 22 patients with a pejorative anatomo-clinical type. The results of the PET/CT were compared with histology and clinical follow-up.

Results

In 23 cases, thyroglobulin (Tg) was positive (14% of TgAb+ Tg+) while in other 131 cases, stimulated Tg was negative (86% of TgAb+ Tg−). Twenty-nine patients (18%) were finally diagnosed with persistent or recurrent disease during follow-up. Independent predictive factors were: age higher than 60 years, Tg+, increase of TgAb concentration in the first year following surgery, and T3/T4/N1 status. PET/CT showed sensitivity of 66% and specificity of 90%. Positivity of PET/CT was significantly associated with a poor prognosis.

Discussion and conclusion

There is no significant association between persistence of TgAb and persistent/recurrent disease when stimulated Tg is negative. An increase of TgAb concentration in the first year of follow-up is an important prognostic indicator. PET/CT with FDG seems to be very useful in the therapeutic management of differentiated thyroid cancer, especially for the patients with pejorative anatomo-clinical types.