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Positive TgAb titer within year of treatment linked to recurrent disease in PTC
In patients with papillary thyroid carcinoma, testing positive for circulating anti-thyroglobulin antibodies in the blood within the first year after primary treatment suggests increased likelihood for recurrent or persistent disease, according to study findings.
In the multicenter, retrospective study, researchers evaluated data from 10 hospital-based referral centers. The study population consisted of 220 patients (mean age, 45.9 years; 85% women) who were diagnosed with papillary thyroid carcinoma (PTC) between 1990 and 2009. These patients also had positive serum anti-thyroglobulin antibody (TgAb) titer in the year after primary PTC treatment. Treatment consisted of total or near-total thyroidectomy, possibly with cervical lymph node dissection and/or radioiodine ablation. Eligible study patients were required to have complete follow-up data available at their 1-year postoperative visit.
A control group consisting of 1,020 patients with PTC had serum TgAb titers that were repeatedly negative for the duration of postoperative follow-up. In both groups, TgAb status was categorized based on the specific test and cutoff values followed by the referral center caring for the patient. The researchers compared tumor characteristics and long-term outcomes (follow-up, 2.5 to 24.8 years) between the two groups and also evaluated the prognostic impact of early normalization of TgAb titers in the TgAb-positive group.
The researchers found that compared with the TgAb-negative controls, the TgAb-positive study cohort had a higher baseline proportion of high-risk patients (study group, 6.9% vs. control group, 3.2%; P<.04) and a higher prevalence of tumors extending beyond the thyroid (study group, 28.2% vs. control group, 24%; P<.0001). At the 1-year visit, the study group also had a higher prevalence of persistent disease than the control group (13.6% vs. 7%; P=.001) and a higher proportion of recurrences at ensuing follow-up visits (5.8% vs. 1.4%; P=.0001). At final follow up, there was a significant difference between the two groups in the proportion of patients with persistent disease or recurrence (6.4% of TgAb-positive patients vs. 1.7% of TgAb-negative patients; P<.0001).
At the 1-year visit, titers were undetectable in 85 of the 220 TgAb-positive patients. There was a significantly lower rate of disease persistence in these patients vs. those who remained TgAb-positive (8.2% vs. 17.3%; P=.05).
According to the researchers, the correlation between PTC aggressiveness and TgAb status was apparent at every time point of the study.
"The differential aggressiveness could already be observed at the time of primary treatment, when the percentage of high-risk patients in the study cohort was twice as high as that of controls," the researchers wrote. "It was also evident at the 1-year follow-up visit, when persistent and recurrent disease rates were approximately two and three times higher, respectively, than those of controls, and at the final follow-up visit, when the disease rate was roughly three times higher than that of the patients who had never presented TgAb positivity."
Disclosure: The researchers report no relevant financial disclosures.