Prevalence of occult level 2b nodal metastases in cN0 squamous cell carcinoma of the oral cavity: A systematic review and meta-analysis.

Elective neck dissection of levels I, II and III is being increasingly used for detecting occult node metastases in patients with oral squamous cell carcinoma (OSCC) and clinically negative neck (cN0). The most frequent potential long-term complication of this procedure is shoulder dysfunction, because of micro- or macroscopic damage to the spinal accessory nerve (SAN). In particular, many studies have reported an association between SAN damage and dissection of level 2b. Furthermore, level 2b dissection is a technically demanding and time-consuming procedure. Our study aims to clarify whether level 2b sparing in cN0 patients with OSCC can be oncologically justifiable. The PubMed, Cochrane and Scopus databases were searched by three different authors for articles on this topic. The primary endpoint of the meta-analysis was the overall prevalence of occult metastases in cervical level 2b nodes in patients with OSCC and clinically negative neck. The meta-analysis was performed using R version 4.0.1. A total of 13 studies and 937 patients were included. The cumulative rate of occult nodal metastases in level 2b was 0.8% (n = 937, 95% CI: 0.1% - 2.2%, τ2  = 0.004). No isolated level 2b metastases was found among the patients with positive level 2b, and in the six studies that reported this association, all patients with nodal disease in level 2b had a positive level 2a. This meta-analysis highlights how level 2b can be safely spared in supraomohyoid neck dissection (SOHND) of patients with OSCC and clinically negative neck, reducing the risk of postoperative shoulder dysfunction.