Abstract
PurposeTo study the pattern of mandibular involvement and its impact on oncologic outcomes in patients with gingivo-buccal complex squamous cell carcinoma (GBC-SCC) and propose a staging system based on the pattern of bone involvement (MMC: Marrow and mandibular canal staging system) and compare its performance with the 8th edition of the American Joint Committee on Cancer (AJCC8).MethodsThis retrospective observational study included treatment-naïve GBC-SCC patients who underwent preoperative computed tomography (CT) imaging between January 1, 2012, and March 31, 2016, at a tertiary care cancer center. Patients with T4b disease with high infratemporal fossa involvement, maxillary erosion, and follow-up of less than a year were excluded. The chi-square or Fisher’s exact test was used for descriptive analysis. Kaplan–Meier estimate and log-rank test were performed for survival analysis. Multivariate analysis was done using Cox regression analysis after making adjustments for other prognostic factors. p-Value <0.05 was considered as significant. Based upon the survival analysis with different patterns of bone invasion, a new staging system was proposed “MMC: Marrow and mandibular canal staging system”. “Akaike information criterion” (AIC) was used to study the relative fitted model of the various staging (TNM staging—AJCC8) with respect to survival parameters.ResultsA total of 1,200 patients were screened; 303 patients were included in the study. On radiology review, mandibular bone was involved in 62% of patients. The pattern of bone involvement was as follows: deep cortical bone erosion (DCBE) in 23%, marrow in 34%, and marrow with the mandibular canal in 43% of patients. Patients with DCBE and no bone involvement (including superficial cortical) had similar survival [disease-free survival (DFS) and locoregional recurrence-free survival (LRRFS)], and this was significantly better than those with marrow with or without mandibular canal involvement (for both DFS and LRRFS). Patients with DCBE were staged using the MMC, and when compared with the AJCC8, the MMC system was better for the prediction of survival outcomes, as AIC values were lower compared with those of the AJCC8. There was a significant association (p = 0.013) between the type of bone involvement and the pattern of recurrence.ConclusionsFor GBC-SCC, only marrow with or without mandibular canal involvement is associated with poorer survival outcomes. As compared with the AJCC8, the proposed Mahajan et al. MMC staging system downstages DCBE correlates better with survival outcomes.
Highlights
Squamous cell carcinoma is the most common histology of the oral cavity cancers
This is a retrospective study on treatment-naïve gingivo-buccal complex squamous cell carcinoma (GBC-SCC) patients who underwent preoperative CT imaging between January 1, 2012, and March 31, 2016, at a tertiary care cancer center
The results of our study show that T classification based upon the marrow mandibular canal (MMC) staging was a better predictor of overall survival (OS), Disease-free survival (DFS), and locoregional recurrence-free survival (LRRFS) as compared with the AJCC8 (Table 5)
Summary
Squamous cell carcinoma is the most common histology of the oral cavity cancers. There are a multitude of factors that impact the prognosis of patients with these tumors. Some studies have reported that tumor size and marrow invasion are independent predictors of reduced survival [13, 17–19]. In view of such varied evidence and lack of clarity, this study aims to evaluate the association of various patterns of mandibular bone involvement and their impact on survival. We endeavored to develop a staging system that would reflect the implications of various types of bone invasion-superficial cortical erosion (erosive bony involvement), deep cortical erosion (infiltrative bony involvement), marrow involvement (infiltrative bony involvement), and mandibular canal involvement (infiltrative bony involvement), as assessed on imaging in a better way
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