Prognostic factors and impact of bone invasion in T1/2 size (<4 cm) gingival squamous cell carcinoma

The aim of this study was to characterize the clinicopathological features and prognostic factors of T1/2 size (<4 cm) gingival squamous cell carcinoma (SCC) and to verify the impact of bone invasion. This was a single-centre, retrospective cohort study involving 206 patients with gingival SCC (maxilla or mandible), treated between 2000 and 2020. The patients were divided into three subgroups based on tumour size and bone invasion. The 5-year overall survival (OS) and disease-free survival (DFS) were 80.6% and 67.6%, respectively. Histological differentiation, advanced T stage, positive resection margin, bone invasion, and postoperative adjuvant therapy were associated with a poor prognosis (P < 0.05). Multivariate Cox analysis indicated that only histological differentiation (hazard ratio (HR) 2.68, P = 0.007) and bone invasion (HR 2.08, P = 0.036) were significantly associated with DFS. Bone invasion was observed in 145 (70.4%) patients, of whom 43 (20.9%) had a T1/2 size tumour. The subgroup with bone invasion and T1/2 size showed significantly worse OS and DFS when compared to the subgroup without bone invasion and similar or worse survival when compared to the subgroup with bone invasion and T3/T4 size. Histological differentiation and bone invasion were poor prognostic factors for gingival SCC, even in cases with small-sized tumours. For suspected bone invasion in small-sized tumours, an adequate bone margin is necessary and postoperative adjunctive therapy needs to be considered.