Significance of "de novo" appearance of thyroglobulin antibodies in patients with differentiated thyroid cancer.

OBJECTIVE: Clinical and laboratory guidelines recommend thyroglobulin antibodies (TgAbs) measurement with every thyroglobulin (Tg) measurement for the follow-up of differentiated thyroid cancer (DTC) patients. However, no evidence exists on the need for perpetual TgAbs testing in patients who are TgAb-negative at baseline. Our study was carried out to evaluate the prevalence, the dynamic changes, and the clinical significance of TgAbs that appeared de novo during the follow-up of DTC patients who were TgAb-negative at baseline.

METHODS: The data of DTC patients with negative pre-ablation TgAbs were reviewed retrospectively. The main characteristics of patients with both transient and sustained de novo TgAbs appearance were analyzed. DTC patients with persistently negative TgAbs served as controls.

RESULTS: Among 119 patients with pre-ablation negative TgAbs, 14 cases (11.7%) with de novo TgAbs appearance (10 and 4 patients with a transient and sustained de novo TgAbs appearance, respectively) were detected. No differences in disease-free survival were observed in patients with de novo TgAbs appearance compared to controls. The TgAbs peak value was higher in patients with sustained de novo appearance compared to patients with transient de novo. Two of 14 patients with de novo TgAbs developed structural disease with concurrently detectable Tg in both cases.

CONCLUSIONS: Transient de novo TgAbs appearance is not infrequent during DTC patients' follow-up, and it has no apparent clinical impact. Sustained de novo TgAbs appearance is rare and may predict structural recurrences; however, similar disease-free survival was observed in patients with sustained de novo TgAbs and TgAb-negative DTC patients.