Endocrine Abstracts (2018) 56 P1157 | DOI: 10.1530/endoabs.56.P1157

Serum thyroglobulin (sTg) before surgery in euthyroid patients with differentiated thyroid cancer (DTC)

Miguel Paja1, Aitzol Lizarraga1,2, Amaia Expósito1, M Teresa Gutiérrez1, Borja Barrios1, Natalia C Iglesias1, Alba Zabalegui1, Cristina Arrizabalaga1, Adela L Martínez3 & Amelia Oleaga3

1Basurto University Hospital, Bilbao, Spain; 2Basque Country University, Biilbao, Spain; 3Amelia Oleaga., Bilbao, Spain.

sTg is universally accepted as the best marker of disease status in DTC. Its presurgical serum level may suggest the presence of distant metastasis in case of very high level, but the correlation between its level and the characteristics of the tumour is yet to be defined.

Objective: To evaluate preoperative thyroglobulin as predictor of DCT features.

Methods: Preoperative sTg was measured in patients operated for DTC between 2011–2017. Patients with positive anti-Tg Ab, treated hypothyroidism, not controlled hyperthyroidism or controlled autoinmune hyperthyroidism were excluded. We evaluated the influence of extrathyroidal extension (ETE), positive lymph node (LN), cytological variant (CV), BRAF mutation, ATA 2015 risk and multifocality on sTg levels. sTg divided (adjusted) by thyroid weight (sTg/weight in grams) after thyroidectomy was also considered in order to reduce the effect of Tg secretion by non-neoplastic tissue, as well as its value corrected by TSH concentration and tumour size (main focus or global size).

Results: 130 CDT (4 FTC, 126 PTC) were included. Median presurgical sTg was significantly lower in DTC with ETE (59.2 vs 106 ng/ml; P<0.04), and the difference persisted when corrected by preoperative TSH (27.1 vs 50.5), glandular weight (2.3 vs 4.5), both parameters (1.2 vs 2.6) as when divided by bigger size (sTg/BS) (5.3 vs 8.5) or global size (sTg/GS) of DTC (2.3 vs 3.5). The differences persisted when preoperative TSH adjusted sTg/BS and sTg/GS. Total and corrected sTg also showed significant differences when DCT were grouped by LN (lower when positive), CV (lesser in classical in opposite to follicular variant), BRAF V600E (lower if present) and ATA2015 risk (lower in intermediate risk versus low risk). Multifocal neoplasm showed no difference in sTg levels when compared with DCT with a single lesion. There were 8 high risk DTC (ATA2015): 2 FTC (one with pulmonar metastasis and other with extensive vascular invasion), and 6 PTC:, one metastatic, 4 with lymph nodes larger than 30 mm and one with gross extrathyroidal invasion, all diagnosed before surgery. These patients collected the highest level of sTg. C - DTC aggressiveness defined by ETE, BRAF V600E positive, pN1 and ATA risk, associates less efficient thyroglobulin secretion, both gross value and TSH corrected levels. This parameter may be a helpful tool for surgical planning, demanding a thorough approach in DCT with low levels of sTg.