Meta-analysis pN+/cN0
In the nine studies, neck staging was determined by a combination of PET, MRI, US and/or CT. Of these 191 patients with TBSCC and cN0 necks, there were 21 cases were pN+/cN0, with a pooled rate of occult metastases of 11% (95% CI: 7%-17% – Figure 2); with corresponding levels of neck dissected known in 11 patients. No publication bias emerged by inspection of funnel plot (Supplementary Figure 1.A). Influence analysis did not report substantial modification when one study was omitted at a time, with pooled proportion ranging from 9% when McRackan was excluded to 14% when Masterson was excluded (Supplementary Figure 1.B). Of the 191 patients included in the meta-analysis, 121 patients had data available on the Tumour stage according to the Pittsburgh classification: 21 cases were pT2 with a pooled rate of occult metastases of 3% (95% CI: 0%-21%), 27 cases were pT3 with a pooled rate of occult metastases of 12% (95% CI: 1%-60%), and finally 65 cases were pT4 with a pooled rate of occult metastases of 14% (CI: 7%-25%) (Figure 3).