Tumour thickness as a predictor of nodal metastases in oral cancer: Comparison between tongue and floor of mouth subsites

Objectives: To identify whether tumour thickness as a predictor of nodal metastases in oral squamous cell carcinoma differs between tongue and floor of mouth (FOM) subsites. Materials and methods: Retrospective review of 343 patients treated between 1987 and 2012. The neck was considered positive in the presence of pathologically proven nodal metastases on neck dissection or during follow-up. Results: There were 222 oral tongue and 121 FOM tumours. In patients with FOM tumours 2.1-4 mm thick, the rate of nodal metastases was 41.7%. In contrast, for tongue cancers of a similar thickness the rate was only 11.2%. This increased to 38.5% in patients with tongue cancers that were 4.1-6 mm thick. Comparing these two subsites, FOM cancers cross the critical 20% threshold of probability for nodal metastases between 1 and 2 mm whereas tongue cancers cross the 20% threshold just under 4 mm thickness. On logistic regression adjusting for relevant covariates, there was a significant difference in the propensity for nodal metastases based on tumour thickness according to subsite (p = 0.028). Conclusion: Thin FOM tumours (2.1-4 mm) have a high rate of nodal metastases. Elective neck dissection is appropriate in FOM tumours >= 2 mm thick and in tongue tumours >= 4 mm thick. (C) 2014 Elsevier Ltd. All rights reserved.