Oral tongue carcinoma: prognostic changes according to the updated 2020 version of the AJCC/UICC TNM staging system

BACKGROUND: This study aimed to evaluate the performance of the 2017 8(th) TNM edition and the latest update in 2020 compared to the 7(th) in a large cohort of patients affected by oral tongue squamous cell carcinoma (OTSCC), considering all stages. MATERIALS AND METHODS: The cohort involved 300 patients affected by OTSCC treated with surgery. All cases were classified according to the 7(th), 8(th) (2017), and the latest updated TNM edition (October 2020),. Patients were grouped based on the shift in tumour (T) category, lymph nodal (N) category and final pathological stage. Overall survival (OS) and disease-free survival (DFS) were calculated with the Kaplan-Meier method. Univariate and multivariate analyses were carried out. RESULTS: According to the 7(th) edition, multivariate analysis OS revealed that stage IV patients had an almost 4-fold risk of death compared to stage I (HR = 3.81 95% CI: 2.32-6.25; p < 0.001). Regarding DFS, stage IV patients had a 2-fold greater risk of relapses, or second primary, than patients in stage I (HR = 2.51 95% CI: 1.68-3.74; p < 0.001). According to 2017 8(th) edition for OS, stage IV patients presented a 5-fold higher risk of death compared to patients in stage I (HR = 5.18 95% CI: 2.96-9.08; p < 0.001) and almost 4-old greater risk of relapses or second primary compared to patients in stage I considering DFS (HR = 3.61 95% CI: 2.28-5.71; p < 0.001). Regarding the recent edition of 8(th) TNM (2020), stage IV patients had an almost 5-fold greater risk of death compared to patients in stage I considering OS (HR = 4.84 95% CI: 2.74-8.55; p < 0.001), while for DFS they had 3-fold greater risk of relapse or second primary compared to patients in stage I (HR = 3.13 95% CI: 1.99-4.91; p < 0.001). CONCLUSIONS: This study confirmed that the recent update of the 8th edition of the TNM (2020) improves stratification and identification of advanced tumours, reducing the number of T3 compared to the 2017 edition and increasing the number of patients with pT4. This improvement made by the updated edition may reduce the risk of skipping adjuvant therapy.