Background: The treatment of the negative neck (N0) in oral cavity squamous cell carcinoma (OCSCC) patients is an ongoing historical debate. Nowadays, an elective Neck dissection (END) is the treatment of choice regarding the neck in most cases of OCSCC, even in early stage (T1-2) disease. However, the extent of the END is still debateable. While most studies regard selective neck dissection (SND) of levels I-III as sufficient for the treatment of the negative neck (N0), others find it as inadequate due to occult skip metastasis to level IV. The aim of this study was to provide level I evidence on the rate of “skip metastases” to level IV in patients diagnosed with N0 OCSCC undergoing various types of END using a meta-analysis of all published studies.
Methods: A comprehensive search of online databases MEDLINE, EMBASE, Cochrane, Scopus and Google scholar for studies published between January 1 1970 and January 1 2018 was carried out. Studies that reported the rate of skip metastasis in patients with N0 OCSCC were included in the meta-analysis. Ninety-seven full-text articles were found eligible for analysis. Only studies that allowed the extraction of data on the rate of true skip metastasis (positive pathological level IV nodes with negative nodes in levels I-III, in clinically N0 patients) were included in the meta-analysis.
Results: Nine retrospective and two prospective studies with a total number of 1022 of patients that reported the rate of skip metastasis to level IV in N0 OCSCC patients met our stringent inclusion criteria. The result of the meta-analysis showed that the true rate of “skip metastases” to level IV in N0 OCSCC patients is extremely low and ranged from 0% to 4% (fixed effects model 0.0027 95% confidence interval [CI] =0.0000-0.0090). The rate of lymph node metastasis to level I, II and III in N0 OCSCC patients were as high as 30.2%, 26.6% and 15.8%, respectively. In a subgroup analysis, various T scores did not show differences in the rate of skip metastasis to level IV. Analysis according to the different oral cavity subsites revealed robust data only on oral tongue primaries. The rate of skip metastasis ranged from 0% to 1.9% (fixed effects model 0.0055 95% confidence interval [CI] =0.0000-0.0218).
Conclusion: The findings of this systematic review and meta-analysis indicated that the true rate of “skip metastases” to level IV in N0 OCSCC patients is extremely low. There is no justification to routinely dissect level IV while performing END for N0 OCSCC patients.