(A620) Risk of Contralateral Lymph Node Metastasis in Oral Tongue Squamous Cell Carcinoma

Introduction: Ipsilateral neck assessment remains the standard of care in lateralized oral tongue squamous cell carcinoma (OTSCC). While the American Society of Clinical Oncology advises that an elective contralateral neck dissection may be considered for select patients with a clinically negative (cN0) contralateral neck, definitive guidelines about specific clinical and tumor factors that predict contralateral neck metastasis are lacking. This study aims to assess the incidence of contralateral lymph node metastasis and to identify associated clinicopathologic risk factors.

Methods: Utilizing the Leaf database, patient records from a single institution were collected from 2014 to 2024. Characteristics included tumor depth of invasion (DOI), midline involvement, differentiation, worst pattern of invasion (WPOI), lymphovascular invasion (LVI), perineural invasion (PNI), pT stage, smoking history, and alcohol use history. All statistical analyses were performed using RStudio.

Results: Of 475 patients with OTSCC, 7.6% had contralateral lymph node metastasis confirmed on surgical pathology. Among these, 80% had a tumor DOI ≥0.4 cm, 10% had tumors with midline involvement, and 80% had a smoking history. Significant associations were found between contralateral lymph node involvement and PNI (p = 0.008), with strong associations for smoking history and PNI (OR and RR = ∞). Tumor depth of invasion showed a moderate association (OR = 1.93, RR = 1.81). Larger contingency table analyses showed significant associations between contralateral lymph node involvement and both poorly differentiated tumors (p = 0.0036) and pathologic T stage (p = 0.0014).

Conclusions: The incidence of contralateral lymph node metastasis in this population was found to be 7.6%. The clinicopathologic risk factors most highly associated with contralateral metastasis were presence of PNI, poorly differentiated tumors, and more advanced pT stage. These findings can provide support for surgeons in treating OTSCC. Further investigation is needed to assess whether any of these factors play a role in regional failure in the contralateral neck.