CT-defined posterior extension predicts pathological nodal metastasis in lower oral cavity squamous cell carcinoma.

BACKGROUND: Anatomical tumor compartmentalization along the anteroposterior axis may influence metastatic behavior in lower oral cavity squamous cell carcinoma (LOCSCC). We developed a computed tomography (CT)-based classification of posterior tumor extension and evaluated its association with pathological nodal metastasis and survival outcomes. METHODS: A retrospective cohort of 76 patients with surgically treated LOCSCC undergoing neck dissection was analyzed. Tumors located posterior to three reproducible CT reference lines were classified as posterior-to-posterior-most (PPP). Multivariable logistic regression assessed the independent association between PPP classification and pathological nodal metastasis (pN+), adjusting for depth of invasion (DOI). Cox proportional hazards models evaluated overall survival (OS) and disease-specific survival (DSS) adjusting for DOI and extranodal extension (ENE). RESULTS: PPP tumors accounted for 38.2% of cases and were strongly associated with nodal metastasis. On multivariable analysis (n = 64), PPP classification remained independently associated with pN+ (OR 24.98; 95% CI 4.75–131.37; p < 0.001). In survival analyses, ENE emerged as the strongest independent predictor of DSS (HR 6.23; p = 0.002), and DOI > 10 mm was also associated with worse DSS. PPP classification did not retain independent significance for OS or DSS after adjustment. CONCLUSIONS: CT-defined posterior extension represents a strong independent preoperative predictor of pathological nodal metastasis in LOCSCC. Although its impact on survival appears mediated by ENE and DOI, PPP classification may provide clinically relevant information for risk stratification, particularly in the management of the clinically N0 neck.