Table 2 Multivariable analysis of predictors for level IB LNs metastases at diagnosis in 1438 patients

Age, ≧50 years vs. <50 years

0.78–2.94

.219

T classification, T4 vs. T1-3

0.53–2.52

.708

Nasal cavity involvement, (+) vs. (−)

0.65–2.64

.446

Oropharynx involvement, (+) vs. (−)

1.18–5.69

.018

Positive RLNs, (+) vs. (−)

0.86–9.50

.088

Positive CLNs, (+) vs. (−)

0.80–8.01

.113

LN necrosis, (+) vs. (−)

0.59–2.52

.594

LNs with ES, (+) vs. (−)

0.27–1.19

.131

D_LN-IIa ≥ 20 mm or level IIa LNs with ES, (+) vs. (−)

1.10–4.46

.026

MAD of LNs ≥30 mm, (+) vs.(−)

0.70–3.25

.293

Positive bilateral CLNs, (+) vs.(−)

0.97–3.92

.061

Positive CLNs at supraclavicular fossa, (+) vs. (−)

0.87–4.82

.103