First thyroglobulin level is a predictor of persistent disease in patients with well differentiated follicular thyroid cancer (WDTC)

Objectives To find that if first Tg level (before radio-iodine ablation) could predict risk of persistent disease.

Methods 288 patients with WDTC were included in the study. Six weeks after thyroid surgery, serum TSH, thyroglobulin (Tg) and Anti-thyroglobulin antibody (Anti-Tg Ab) were measured in off-T4 state in one laboratory and patients were treated with radio-iodine and followed up every 6 months. Complete remission, was defined as normal physical exam and neck ultrasonography , negative whole body iodine scan as well as off-T4-Tg<2ng and negative Anti-Tg Ab.

Results 211 female and 77 male with mean age of 40.5 years (±16 ) were included in the study with a mean follow up time of 3.6 years. According to TNM staging 60.4%, 7.5%, 9.1% and 23% of patients were in stage 1, 2, 3 and 4 respectively. Cancer death was noted in 6 patients and persistent disease in 51.8% of patients. Mean age, serum TSH, Anti-Tg ab level ,follow up time and time difference between operation and radio-iodine therapy was not significantly different in patients with and without persistent disease (P>0.3). Also sex ratio and Papillary/follicular ratio was not significantly different in two groups (P>0.2). Mean first Tg level was 234.2 and 27.1 ng/ml in patients with and without persistent disease (P=0.004). Using logistic regression TNM staging and first off-T4 Tg level were the only two variables significant in prediction of outcome of the disease.

Conclusions Our study showed that first thyroglobulin level is a powerful predictor of outcome in patients with WDTC.