International Session 25 　　Equilibrium Research 2

Purpose.To evaluate prognostic value of worst pattern of invasion-5(WPOI-5)for patients with pathologically earlystage and low-risk oral tongue squamous cell carcinoma(OTSCC) .Methods.Patients with early-stage, low-risk OTSCC(n224)treated between 2005 and 2016 were analyzed.WPOI-5, defined as tumor satellites 1 mm from the main tumor or closest satellite, was evaluated for its prognostic impact on cancer -specific survival(CSS)and locoregional recurrence-free survival(LRRFS) .A WPOI-5-based nomogram was also developed for validation.Results.For those with WPOI-5, the 5-year CSS and LRRFS were significantly inferior to those without WPOI-5(both p