Lymphovascular invasion is associated with survival for papillary thyroid cancer.

Data are limited regarding the association between tumor lymphovascular invasion and survival for patients with papillary thyroid cancer (PTC). This study sought to examine lymphovascular invasion as an independent prognostic factor for patients with PTC undergoing thyroid resection. The National Cancer Data Base (2010-2011) was queried for patients with PTC who underwent total thyroidectomy or lobectomy. Patients were classified into two groups based on the presence/absence of lymphovascular invasion. Demographic, clinical and pathological features were evaluated for all patients. A Cox proportional hazards model was utilized to identify factors associated with survival. Results show that 45,415 patients met inclusion criteria; 11.6% had lymphovascular invasion. Patients with lymphovascular invasion were more likely to have larger tumors (2.8cm vs 1.5cm, P<0.01), metastatic lymph nodes (74.1% vs 32.5%, P<0.01), and distant metastases (3.0% vs 0.5%, P<0.01). They were also more likely to receive radioactive iodine (69.3% vs 44.9%, P<0.01). Unadjusted overall 5-year survival was lower for patients who had tumors with lymphovascular invasion (86.6% vs 94.5%) (log-rank P<0.01). After adjustment, increasing patient age (HR=1.06, P<0.01), male gender (HR=1.68, P<0.01), presence of metastatic lymph nodes (HR=1.77, P<0.01), distant metastases (HR=3.49, P<0.01), and lymphovascular invasion (HR=1.88, P<0.01) were associated with compromised survival. For patients with lymphovascular invasion, treatment with RAI was associated with reduced mortality (HR=0.43, P<0.01). The presence of lymphovascular invasion among patients with PTC is independently associated with compromised survival. Patients who have PTC with lymphovascular invasion should be considered higher risk, and adjuvant RAI should be more strongly considered.