Rate of occult metastasis in lip squamous cell carcinoma: A systematic review and meta-analysis

Objectives: The rate of occult metastasis in lip cancer is poorly studied. Management of the regional nodal basin in lip cancer is thus controversial. This study sought to understand the true rate of micrometastasis in lip cancer.

Materials and methods: Systematic review and meta-analysis was conducted of English language studies reporting lip cancer sentinel node biopsy results. Studies were obtained from the PubMed database between the years 2000 and 2023 using the search terms "sentinel node biopsy" and "squamous cell carcinoma." Random effect and fixed effect meta-analyses were performed.

Results: Thirteen studies met inclusion criteria. Low heterogeneity was noted among the studies, as indicated by the I² inconsistency test (I² = 0%). The rate of occult metastasis ranged between 0 and 33% (mean 9%). A total of 189 lip sentinel node biopsies had been performed. Of these, 21 revealed occult nodal metastasis (11.1%, 95% CI 7.36%-16.44%). One step, generalized linear mixed modeling revealed the true rate of occult nodal metastasis to be 10% (95% CI (0.0504, 0.1746), p < 0.0001).

Conclusion: The rate of occult metastasis in lip cancer approaches the threshold for elective management of the regional nodal basin. Sentinel node biopsy is optimally suited for management of high-risk early T stage lip cancer.