Incidence and impact of skip metastasis in the neck in early oral cancer: Reality or a myth?

Objectives: Varying evidence exists surrounding skip metastasis in clinically node-negative oral cancer. We aim to report its incidence, identify factors predicting its presence, and determine survival outcomes to possibly decide "adequacy" of neck dissection for this select group.

Methods: A review of audit records (clinical and pathologic) was undertaken to identify early stage (cT1/T2 cN0) oral squamous carcinoma patients operated between January 2016 and December 2020. Skip metastasis was defined as presence of nodal metastases distant from the primary tumour and at a lower level without metastases at levels above this. The factors predicting its presence were determined using chi-square and multivariate tests. Survival analysis was performed using Kaplan-Meier and regression hazard models.

Results: Occult metastasis rate was 17.9 % among 761 patients, with 47.1 % travelling to level I. Skip metastasis at level III was seen in 1.2 % and level IV was 0.3 %. Presence of PNI predicted the presence of skip metastasis at level III (p = 0.041, OR-0.241, 95 %CI 0.062-0.942) and no significant factors were identified for level IV. The 5-year disease-free survival was significantly reduced with isolated level IV metastasis (50 % vs 79.6 %, p = 0.017). Isolated occult metastasis at level Ia was in 0.3 %, all from tongue cancers. Their presence did not impact the 5-year overall survival (100 % vs 90.7 %, p = 0.628) and disease-specific survival (100 % vs 92.5 %, p = 0.675).

Conclusion: The negligible incidence of skip metastasis to level IV in a clinically node negative neck suggests that clearance up to level III might be adequate in a large majority of patients.