Does medullary vs. cortical invasion of the mandible affect prognosis in patients with oral squamous cell carcinoma?

Abstract Objectives It is still under debate whether mandibular involvement by oral squamous cell carcinoma (OSCC) could be identified as a factor for cancer staging and prognosis prediction. In addition, the influence of different types of mandibular invasion (cortex or medullary invasion) on patients’ prognosis is still unclear. The aim of our systematic review was to establish whether the mandible invasion or its subset should be considered an independent prognostic factor for patients with OSCC. Materials and Methods According to the predesigned inclusion criteria for a systematic review, the search for eligible studies was performed. Mandibular invasion and invasion depth were considered as the primary and secondary predictor variables, respectively. The electronic search was performed using 12 databases. Hand-searching covered 14 related journals and references of the included studies were scanned. The risk of bias assessment was evaluated by two reviewers using risk of bias assessment tools recommended by Saltaji. Two reviewers extracted the data in duplicate. RevMan 5.2 was used for meta-analysis to assess the primary outcomes (disease-free survival and overall survival) and the secondary outcomes (2-year/5-year survival rate and local control). Outcome Eighteen studies were included and used as the study sample. A number of 3756 participants were analyzed. Among these included studies, 7 had unclear risk of bias and the remaining showed high risk. The results of our meta-analyses showed a significant relationship between the mandibular invasion and the overall survival (P=0.04), and most importantly, medullary involvement could reduce the overall survival (P=0.0001) but not cortex involvement (P=0.66). When focusing on the disease specific survival, mandibular medullary involvement predicted a poor disease specific survival (P