Measuring nonstimulated thyroglobulin with a second-generation assay in patients with low or intermediate-risk papillary thyroid carcinoma is sufficient for long-term follow-up, according to a recent analysis.
“To validate the proposal of exempting patients from [thyroglobulin] stimulation, it is fundamental to know the evolution of patients with nonstimulated [thyroglobulin] 0.2 ng/mL when the stimulation test, proposed to be abolished, is no longer performed,” Pedro Weslley Rosario, MD, PhD, of the department of endocrinology at Santa Casa de Belo Horizonte, Brazil, and colleagues wrote. “We confirm that this criterion has a high negative predictive value (98%). This was observed even in patients initially classified as intermediate risk.”
Pedro Weslley Rosario
In a retrospective study, Rosario and colleagues analyzed data from 578 patients with low- or intermediate-risk papillary thyroid carcinoma who underwent total thyroidectomy with or without radioactive iodine therapy (80.2% women; mean age, 48 years). Within the cohort, 47.2% were classified as low risk according to American Thyroid Association guidelines; 52.7% were classified as intermediate risk; 68.3% underwent radioactive iodine therapy. All patients included in the cohort also exhibited an excellent response to initial therapy, defined as nonstimulated thyroglobulin of 0.2 ng/mL or less and negative neck ultrasound; follow-up ranged from 24 to 108 months.
Researchers found that 12 patients (2%) showed disease recurrence; sex, age, tumor stage, risk classification, lymph node status or iodine therapy were not predictors of structural disease.
At the time when disease recurrence was confirmed, nonstimulated thyroglobulin was more than 0.2 ng/mL in 10 of the 12 patients; antithyroglobulin antibodies (TgAb) remained undetectable in 11 patients, and they were detectable but below the reference value in one patient. Neck ultrasound was positive for disease recurrence in nine of the patients. In the two patients without elevated nonstimulated thyroglobulin levels, one had lymph node metastases; one had pulmonary metastases; TgAb levels were undetectable in both.
“Of note, only two cases of structural recurrence were detected after more than 60 months of follow-up,” the researchers wrote.
Among the 560 patients who continued to have thyroglobulin levels of 0.2 ng/mL or less, ultrasound permitted the detection of only one neck recurrence. Measurement of TgAb detected no recurrence, according to researchers.
“Follow-up of patients with thyroid carcinoma of low and intermediate risk and excellent response to therapy can be simplified,” Rosario told Endocrine Today. "We emphasize that our results apply to low- or intermediate-risk patients who have undetectable TgAb and neck ultrasound performed by an experienced professional showing no abnormalities after initial therapy, and when [thyroglobulin] is measured with a second-generation assay.”
The researchers proposed that patients with nonstimulated thyroglobulin levels remaining less than 0.2 ng/mL undergo neck ultrasound at 5 years of follow-up only when at risk for neck recurrence, such as those at intermediate risk with relevant lymph node involvement. – by Regina Schaffer
The researchers report no relevant financial disclosures.