Serum thyroglobulin level measured after thyroxine withdrawal is useful to predict further recurrence in whole body scan-negative papillary thyroid cancer patients after reoperation.

The best treatment option for recurrent papillary thyroid carcinoma (PTC) is reoperation when the recurrent lesion is locoregional. The prognostic significance of serum thyroglobulin (Tg) levels before reoperation and the association between the outcome of reoperation and Tg level remain unclear. Our study aimed to determine the outcomes of patients who underwent reoperation and their association with serum Tg levels. We retrospectively studied 79 patients with PTC with locoregional recurrence whose whole-body scan results were negative for any recurrence but whose serum Tg levels were detectable after first-line treatment. All the patients underwent reoperation and follow-up examinations, which involved serial serum Tg measurements after thyroxine withdrawal (T4-off Tg), neck ultrasonography, chest computed tomography, and/or fluorodeoxyglucose-positron emission tomography, to detect further recurrence. During the median follow-up duration of 89 months (range, 38-332 months), 30 patients (38.0%) experienced a second recurrence even after the reoperation. Among all patients, only 12 whose Tg levels decreased postoperatively to undetectable levels showed no recurrence. Most recurrences were detected in the patients with high T4-off Tg levels after the reoperation (T4-off Tg level (ng/mL), number of patients with recurrence, %: <1, 0/12, 0%; 1-10, 9/31, 33.3%; >10, 16/22, 72.7%; P < 0.001). In conclusion, recurrence occurred in 38.0% of the patients even after the reoperation. The postoperative T4-off Tg level was a good indicator of recurrence after the reoperation. Therefore, patients who experience recurrence should undergo follow-up examinations that involve routine measurements of T4-off Tg levels, especially when postreoperative values exceed 10 ng/mL.