Metachronous contralateral papillary thyroid carcinoma following lobectomy: Incidence, clinicopathological shifts, and survival outcomes in a population-based cohort

Why clinicians should know about it

• Picked for Breast and Endocrine Surgery (paper of the day, 2 November 2026): Long-term contralateral cancer risk after thyroid lobectomy

Abstract

BACKGROUND: Thyroid lobectomy is increasingly utilized for papillary thyroid carcinoma (PTC), yet the long-term risk of metachronous contralateral PTC (MC-PTC) remains poorly characterized. This study evaluated MC-PTC cumulative incidence, risk factors, clinicopathological features versus first primary PTC (FP-PTC), and its association with survival. METHODS: Patients with PTC undergoing initial lobectomy in 2004-2017 were identified from the Surveillance, Epidemiology, and End Results 17 registries database. MC-PTC was defined as a newly diagnosed PTC ≥6 months after lobectomy. Cumulative incidences accounting for competing risks were calculated. Multivariable Fine-Gray subdistribution hazard models identified risk factors. McNemar-Bowker tests assessed paired clinicopathological shifts. Multivariable time-dependent Cox regression models evaluated MC-PTC's association with overall survival (OS) and disease-specific survival (DSS), with MC-PTC modeled as an internal time-dependent covariate. Sensitivity analyses repeated all primary analyses using alternative 3- and 12-month MC-PTC definitions, and included a T1a-T1b subgroup for incidence and risk-factor analyses, a Cox model for MC-PTC risk, and a paired T-stage analysis limited to diagnoses by 2017. RESULTS: Among 14,058 patients (median follow-up, 126 months), 177 (1.3%) developed MC-PTC after a median of 41 months. The 5-, 10-, 15-, and 20-year cumulative incidences were 0.8%, 1.2%, 1.5%, and 1.7%, respectively. In multivariable analyses, aggressive histological variants were associated with higher MC-PTC risk (subdistribution hazard ratio [sHR] 3.44, 95% confidence interval [CI] 1.09-10.81, P = 0.04), whereas older age (≥65 vs. <35 years: sHR 0.46, 95% CI 0.26-0.80, P = 0.006) and more advanced T stage (T3 vs. T1a: sHR 0.20, 95% CI 0.06-0.60, P = 0.004) were associated with a lower risk. Paired analysis revealed shifts in T (P = 0.03) and N stages (P < 0.001), but histological grouping remained stable (P = 0.67). MC-PTC was not significantly associated with OS (adjusted HR 0.82, 95% CI 0.46-1.44, P = 0.48) or DSS (adjusted HR 2.48, 95% CI 0.61-10.14, P = 0.21). Sensitivity analyses supported the incidence, risk-factor, and survival findings, whereas the T-stage paired finding was less robust. CONCLUSIONS: MC-PTC is infrequent after lobectomy. Although paired analyses suggested modest clinicopathological stage shifts compared with FP-PTC, MC-PTC does not appear to adversely affect long-term survival. These findings suggest that concern regarding future MC-PTC should not, by itself, preclude lobectomy in appropriately selected patients and that management should be individualized.

Abstract as published, via PubMed.