Relationship of biochemically persistent disease and thyroglobulin-doubling time to age at surgery in patients with papillary thyroid carcinoma.

In patients with papillary thyroid carcinoma (PTC), detectable serum thyroglobulin (Tg) after total thyroidectomy implies biochemically persistent disease (BPD). We reported that the thyroglobulin-doubling time (Tg-DT) was a potent prognostic indicator in patients with BPD. To identify factors that are related to BPD and Tg-DT, we performed new analyses on the data gathered in our previous study. Using the data of 426 patients with PTC in whom the Tg-DT was computed after total thyroidectomy, multivariate logistic analyses for BPD and Tg-DT were performed. Postoperatively, 142 (33%) patients had BPD. The percentages of BPD patients were significantly higher among the young (<40 years) and elderly (≥60 years) patients compared to the middle-aged patients (41%, 41%, and 27%, respectively). Multivariate analysis showed that cN1b, tumor size ≥4 cm, and Ex2 were significantly associated with BPD. The percentage of patients with Tg-DT <2 years among the BPD patients increased with age: 6% in the young, 15% in the middle-aged, and 47% in the elderly patients. Multivariate analysis of the BPD patients revealed that Tg-DT was associated only with the age at surgery. The current analyses indicate that BPD is significantly correlated with the extent of disease status and that Tg-DT correlates only with patient age at surgery. Although our results clearly indicate that the biological behavior of PTC is age-related, the underlying reason for this remains to be established.