RESULTS: 101 patients (48.8%) had presence VPI, and 106 patients (52.2%) without. Median follow-up was 40.5 months. The 5-year overall survival rate was 80.0% and 63.6% for those with tumor size smaller than 3cm and tumor size ranged 3-5cm, respectively. Kaplan-Meier survival analysis stratified by tumor size showed worse overall survival in patients with VPI (P=0001). And survival rates decreased when the size of the tumor increased (p=0.001). There was a significant effect for the VPI and tumor size (rang 3 to 5cm) interactions for OS (p=0.006), the effects of VPI for other tumor size groups were not significant. Overall survival between tumor size ranged 3-5cm with VPI and tumor size ranged 5-7cm without VPI was not significant (p=0.192). In multivariate analysis, VPI, larger tumor size, older age were significantly associated with decreased OS.