Contralateral sentinel node drainage patterns in early lateralised oral squamous cell carcinoma - a retrospective study

Sentinel node biopsy (SNB) maps tumour draining lymph nodes on an individual basis, identifying locations outside typical neck dissection levels including the contralateral neck. We report contralateral drainage and positivity rates in lateralised early oral cavity squamous cell carcinoma (OCSCC) and assess associations with tumour characteristics. This was a single-centre retrospective study of patients with lateralised cT1-T2 OCSCC treated with wide local excision and SNB between February 2016 and January 2022. Data included tumour depth, distance to the midline, lymphatic drainage, sentinel node number/location and SNB status. Variables were analysed using two-tailed Student t-test and Fisher's exact test, with Holm-Bonferroni correction where appropriate. Ninety-two patients underwent SNB; 64 met the criteria for lymphatic drainage analysis. Contralateral or bilateral drainage occurred in 26 (40.6%) cases. Fifty (78.1%) tumours involved the anterior 2/3 tongue, with contralateral or bilateral drainage in 20 (40.0%). Twenty-two patients (34.4%) had positive SNB, including three (4.7%) with contralateral metastases. Mean follow up was 46.3 months. One- and 3-year overall survival were 93.7% and 77.8%, respectively; disease-free survival was 91.7% and 80.0%, respectively. One patient (1.5%) had a false-negative SNB, and three (4.7%) would have been inadequately staged or treated by ipsilateral elective neck dissection. Contralateral drainage was common in lateralised early OCSCC, although contralateral positivity was uncommon. SNB may improve individualised staging by identifying clinically relevant contralateral drainage not addressed by ipsilateral elective neck dissection. Prospective multicentre studies are needed to define anatomical and tumour-related predictive factors for contralateral drainage.