Tumor depth of invasion and prognosis of early‐stage oral squamous cell carcinoma: A meta‐analysis

Objectives To assess the prognosis for early‐stage oral squamous cell carcinoma according to tumor depth of invasion (DOI). Methods This study was logged in the PROSPERO database under protocol # CRD42017059976. The search was conducted in six electronic databases up to May 2019. Fixed‐effects meta‐analysis was performed for the calculation of the odds ratio (OR) and respective 95% CI. Primary outcomes were lymph node metastasis, recurrence, and survival. Heterogeneity was calculated by the I2 test. The certainty of evidence was assessed by Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) approach. Results Twenty‐seven studies were included (19 in the meta‐analysis) with 2,404 patients with a mean of 60 years of age. High tumor DOI is associated with a greater chance of presenting lymph node metastasis, regardless of the cutoff point for DOI (13 meta‐analysis; OR 1.69–53.08), recurrence (five meta‐analysis; OR 1.22–3.83), and lower chance of survival (1 meta‐analysis; OR 0.49). The certainty of evidence varied from very low to low. Conclusions Tumor DOI is a good prognosticator for early‐stage OSCC. The findings of the current meta‐analysis highlight the clinical relevance of DOI and corroborate its incorporation for staging OSCC.