6058 Background: Depth of invasion (DOI) has been incorporated in the new AJCC TNM staging (8th edition) for oral cancers. We hypothesized that the negative effect of increasing DOI on outcomes was a result of an increased propensity to node metastasis and appropriate neck treatment would negate its detrimental effect on outcomes. Methods: Patients with T1/ T2 oral squamous cell carcinoma, clinically node negative, from a previously reported Randomized Controlled Trial (NCT 00193765) formed the cohort for this study. Patients were restaged according to the new staging system . Overall survival(OS) was estimated by the revised T stage for the entire cohort and separately for those who underwent END and those who did not (TND arm) using Kaplan Meier and log rank test . Multivariate analysis was performed using Cox proportional hazard model making adjustment for neck treatment, T stage, site, prognostic factors and the interaction between revised T stage and neck treatment. Results: Of the 596 patients 577 were evaluable, with a median follow up of 77.57 months. Initial pT staging was pT1, 389(67.4%); pT2, 181(31.4%); pT3, 7(1.2%) and was modified to pT1, 195(33.8%); pT2, 280(48.5%); pT3, 102(17.7%) on restaging . 288 patients underwent END and 289 did not (TND arm). For the entire cohort 5-year OS rates were 79.0% [95 %CI, 73.12-84.88] for pT1, 69.4% [95% CI, 63.91-74.89] for pT2 and 53.0% [95% CI, 43.2 -62.8] for pT3 with significant difference between the 3 groups (p < 0.001). In those without upfront neck treatment( TND ), OS difference was maintained between the pT1 and pT2 groups [81.1% (95%CI, 73.26-88.94) vs 65.0% (95%CI, 56.77-73.23)], p = 0.004. This difference was not apparent in the END arm ,pT1 -76.9% (95 %CI, 68.47-85.33) vs pT2 -73.7% (95%CI, 66.25-81.15), p = 0.73. T3 tumours had uniformly poor survival irrespective of neck treatment. On multivariate analysis of the revised pT1/T2 cohort (n = 475), pT stage, neck treatment and grade were independent prognostic factors impacting OS. There was a significant interaction between the T stage and neck treatment (p = 0.03). Conclusions: When DOI < 10 mm, END supplants the prognostic implication of depth with similar outcomes for T1 and T2 tumours (new AJCC staging). The exact role of DOI on outcomes warrants further research. Clinical trial information: NCT00193765.