Serum tumor markers alone can provide reliable surveillance of patients who undergo total thyroidectomy for low- and intermediate-risk papillary thyroid carcinoma if their thyroglobulin (Tg) level is <1 ng/mL with negative anti-Tg antibodies 1 year after surgery, according to a review published in Clinical Thyroidology.

The results suggest that the current combination of serum tumor markers and cervical neck ultrasound may not always be necessary, which can help reduce healthcare costs.

The study included patients who underwent total thyroidectomy for low- and intermediate-risk papillary thyroid carcinoma at a single academic institution between 2007 and 2014 (n=226). The researchers performed neck dissections and radioactive iodine ablation when clinically indicated.

Patients were categorized as having either undetectable (<0.2 ng/mL) or indeterminate (0.2-0.99 ng/mL) nonstimulated Tg values 1 year after thyroidectomy. The researchers followed-up patients annually with measurements of serum Tg, anti-Tg antibodies, and thyroid-stimulating hormone levels, as well as cervical ultrasound. The primary outcome was sonographically abnormal lymph nodes, as defined by European Thyroid Association criteria, at 3-year and final follow-up visits.

Of 226 patients, 171 had undetectable Tg levels and 55 had indeterminate Tg levels at 1-year follow-up.

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In the undetectable Tg group, the median initial tumor size was 8 mm (interquartile range, 5-12 mm) compared with 9 mm (interquartile range, 4.75-15 mm) in the indeterminate Tg group. Radioactive iodine was administered to 45.6% of patients in the undetectable Tg group vs 52.7% of those in the indeterminate Tg group. The median follow-up was 72 months.

At 1 year after thyroidectomy, the negative predictive value of undetectable Tg was similar to that of indeterminate Tg.

At 3-year follow-up, the researchers found a negative predictive value of 98.8% for patients with undetectable Tg levels, with 2 patients having indeterminate lymph nodes that were not present at the last follow-up assessment. For patients with indeterminate Tg levels, the negative predictive value at 3 years was 98.2%, with 1 patient having an indeterminate lymph node and an increase in Tg to >1 ng/mL.

“The current study suggests that low-risk patients who demonstrate a satisfactory initial treatment response…could be spared the burden of future ultrasound examinations unless warranted by rising tumor markers,” the researchers wrote.

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Reference

Orr LE, Yeh MW, Livhits MJ. Do patients with low- and intermediate-risk thyroid cancer need continuing postoperative neck surveillance ultrasounds? Clin Thyroidol. 2019;31(8):343-345.