Endocrine Abstracts

Rising thyroglobulin (Tg) serum concentration in patients after total thyroidectomy due to differentiated thyroid cancer (DTC) with no pathological radioiodine uptake on posttherapeutic whole-body scan (WBS) constitutes a challenge for physicians dealing with DTC management.

The FDG PET–CT is regarded as a gold diagnostic standard in such cases.

Our aim was to find factors which may help predicting positive PET–CT result, and to evaluate its impact on management decisions.

The study was a retrospective analysis of the results of PET–CT performed in a group of 71 DTC patients. Positive PET–CT result was obtained in 35 cases. PET (+) group showed to differ significantly in many aspects, as age, the most common cancer type and medical history, from the PET (−) one. The PET–CT results were positive in cases of long-term radioiodine treated patients in whom significant Tg rise had been observed, as well as in cases of never-iodine avid metastases. In PET (+) group mean Tg concentration was significantly higher than in PET (−) group (721.6 ng/ml vs 62.2 ng/ml) and Tg 2-year increase was on av. 236.2% in PET (+) while 70.5% in PET (−) group (in endogenous TSH stimulation).

In PET (+) group metastases to neck lymph nodes or neck soft tissues were found in 11 cases, pulmonary metastases in 14 cases, mediastinal lymph nodes were affected in nine cases, one case of liver metastasis and six cases of bone metastases were found. Surgery treatment was offered to ten patients, radiotherapy to six patients, and five patients entered treatment programs with thyrosine kinase inhibitors. Other patients remain in active observation.

Conclusion: PET–CT is a useful diagnostic tool which brings important information with an impact on further treatment of properly selected DTC patients.