Endocrine Abstracts

Background

Papillary thyroid carcinoma (PTC) is the most frequent thyroid malignant neoplasm. American Thyroid Association (ATA) guidelines don’t specify how to follow-up low-risk PTC patients not receiving radioiodine therapy (RAI) after total thyroidectomy (TT). Indeed, there is no consensus among authors regarding the interpretation of thyroglobulin (TG) levels and ultrasound neck (US) findings during follow-up in these settings.

Aim

To evaluate outcome predictive factors in low-risk PTC patients treated with TT but not with RAI.

Patients and methods

This retrospective study was conducted on 61 patients who were followed-up for at least 12 months after TT. Assessment of TG, TG-antibodies (ATG) and US was performed after TT and then every 18-24 months. ATA Guidelines Classification system of response to therapy (excellent, biochemical and structural incomplete, indeterminate) was applied even if RAI was not administered. We define as “suspected disease progression/relapse” (sPR) the appearance/growth of thyroid remnants (TR) by US and/or the detection of increased serum TG and/or ATG levels.

Results

The median follow-up was of 41.6±17 months; 5% of patients showed sPR. A slightly higher risk of sRP was observed in patients ≥ 55 years. All patients with sPR had been diagnosed with a microPTC and presented an indeterminate response during follow-up. No differences concerning sex, age, TNM, histology, thyroiditis history were observed as compared to indeterminate patients without sPR. In patients with indeterminate response, TG and ATG levels were found slightly increasing during follow-up even if TSH target levels were achieved with l-thyroxine therapy. In the whole cohort, during follow-up ATG absence was not associated with increased TG levels; in patients with excellent response, a slight variation in TG levels was likely due to TSH levels fluctuation without sPR development. Most ATG positive patients become negative at the end of follow-up and none of them showed sRP. 63% of patients showed TR disappearance after 15±8 months.

Conclusion

Low-risk PTCs have a favorable outcome and the presence of TR is not a risk factor for relapse. However, microPTC could lead to sPR and careful follow-up is advised especially in older patients. Slight variations in TG levels in ATG/US negative patients could be due to TSH fluctuations rather than sRP development.