Margin Positivity and Survival in Papillary Thyroid Microcarcinoma: A National Cancer Database Analysis

The rising incidence of thyroid cancer has been attributed to increased detection of papillary thyroid microcarcinoma (PTMC). Although some PTMCs are thought to harbor aggressive pathologic features, the clinical significance of these features remains unclear. This study examines factors associated with survival in this patient population.

Adults with PTMC, defined as papillary thyroid carcinoma ≤ 1.0 cm, who underwent thyroidectomy between 2004 and 2016, were identified in the National Cancer Database. Demographic and clinical variables were analyzed. The primary aim was to identify factors associated with survival. The secondary aim was to assess the association of microscopic margins on survival and to identify factors associated with margin positivity. Overall survival was estimated using Kaplan-Meier methods and compared using log rank tests. Cox proportional hazards and binary logistic regression models identified factors associated with survival and margin positivity, respectively.

Of 77,817 patients with PTMC, 13,507 met inclusion criteria; 2,649 (20%) of these patients presented with advanced features: extrathyroidal extension (n = 916, 7%), lymphovascular invasion (n = 398, 3%), lymph node involvement (n = 2,003, 15%), and distant metastasis (n = 39, <1%). Microscopic margin positivity was present in 906 patients and associated with increased risk of death (hazard ratio 1.58, 95% CI 1.04-2.41). Academic facilities (odds ratio [OR] 0.75, 95% CI 0.59-0.95) and operative volume (OR 0.98, 95% CI 0.97-0.98) were associated with decreased margin positivity.

Positive margin status was significantly associated with increased risk of death for PTMC. Higher operative volume and treatment at academic centers were associated with lower rates of margin positivity and may help improve survival outcomes in PTMC patients with aggressive features.