Pathological risk factors stratification in pN3b oral cavity squamous cell carcinoma: Focus on the number of positive nodes and extranodal extension.
According to the AJCC 2017 Staging Manual, oral cavity squamous cell carcinoma (OCSCC) with pN2 disease (based on the AJCC 2010 criteria) and extra-nodal extension (ENE) should be classified as pN3b. We performed a detailed outcome analyses in this patient subgroup. We retrospectively reviewed the clinical records of consecutive OCSCC patients who underwent radical surgery between 1996 and 2017. Patients with pN3b disease (n = 365) were divided into a pN+ ≥8/ENE ≥5 subgroup (defined by the presence of pN+ ≥8 nodes or ENE ≥5 nodes, n = 77) and a pN+ ≤7/ENE ≤4 subgroup (defined by the presence of pN+ ≤7 nodes and ENE ≤4 nodes, n = 288). Patients with pN0/pN1/pN2 (n = 1192/179/197) disease were included for comparison purposes. Patients in the pN+ ≥8/ENE ≥5 subgroup had less favorable 5-year outcomes than those in the pN+ ≤7/ENE ≤4/pN2/pN1/pN0 groups (local control, 64%/79%/86%/83%/88%, p < 0.001; neck control, 55%/75%/80%/86%/93%, p < 0.001; distant metastases, 67%/28%/20%/12%/3%, p < 0.001; disease-free survival, 21%/51%/64%/72%/82%, p < 0.001; disease-specific survival, 25%/55%/71%/82%/92%, p < 0.001; overall survival, 19%/40%/54%/64%/82%, p < 0.001; respectively). Among patients with pN3b disease, multivariable analysis identified the pN+ ≥8/ENE ≥5 subgroup, lower neck (level IV/V) metastases, and depth of invasion ≥25 mm as independent adverse prognostic factors for 5-year distant metastases and survival rates. Patients in the pN+ ≥8/ENE ≥5 subgroup have an unfavorable prognosis and their classification as pN3b is advisable. In contrast, patients in the pN+ ≤7/ENE ≤4 subgroup should be classified as pN3a.