Papillary thyroid cancer: factors involved in restaging N1 disease after total thyroidectomy and radioactive iodine treatment.

Context: The presence of cervical lymph node metastases is a strong predictor of persistent disease in papillary thyroid cancer (PTC).

Objective: The objective of the study was to investigate factors associated with improved outcome in patients with PTC and lymph node metastases.

Design: Retrospective Cohort Setting: The study was conducted at a tertiary university-affiliated medical center.

Patients: PATIENTS treated for PTC and N1 disease since 1995 participated in the study. Partial thyroidectomy, distant metastases, and poor differentiation were the exclusion criteria.

Interventions: The intervention was a data search of the Thyroid Registry.

Main Outcome Measures: Significant association of clinical and disease-related factors with persistent disease was measured.

Results: Of 800 patients treated for PTC during the study period, 182 (69% female; mean age at diagnosis 46.5 ± 15 y) had N1 disease (47% N1a, 53% N1b). Most (93.4%) had a classical/follicular variant; 65% had T1-2 disease; and 42.6% had extrathyroid extension. All patients were treated with total thyroidectomy and radioactive iodine (mean first dose 147 ± 26 mCi). Lateral neck dissection was performed in 53% patients. Mean follow-up was 9.2 ± 4.5 years. On regression analysis, factors significantly and independently associated with persistent disease at 1 year (94 of 182, 52%; 40% of N1a group, 59% of N1b group) were primary tumor size, focality, and extrathyroid extension and at the last follow-up (62 of 182, 34%; 27% of N1a group, 33% of N1b group), primary tumor size, 1-year stimulated thyroglobulin level, and cumulative I(131) dose. Stimulated thyroglobin less than 2.1 ng/mL at 1 year predicts the absence of disease at the last follow-up with an 86% negative predictive value.

Conclusion: PATIENTS with PTC and N1 disease treated with total thyroidectomy and radioactive iodine have a significant risk of persistent disease at early and late follow-up. The extension of the primary tumor at diagnosis appears to be the only significant predictor of persistency in these patients.