Improved Survival For N2a Oropharynx Squamous Cell Carcinoma Vs. N0/n1: Is Our Staging System Still Accurate? A Population-based Analysis Of 15,588 Cases.

Presentation: S159
Topic: Oropharynx
Type: Oral
Date: Monday, July 18, 2016
Session: 10:45 AM - 12:15 PM Oropharynx II
Authors: Valerie Fritsch, MD, David Neskey, MD, Terry Day, MD
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Institution(s): Medical University of South Carolina
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Background: In the current era, the majority of tonsil and base of tongue (BOT) squamous cell carcinoma (SCC) is related to HPV. HPV-related oropharyngeal SCC is increasingly recognized as a distinct entity (compared to non-HPV-related oropharyngeal SCC) in numerous ways; however, the AJCC staging system has yet to reflect this distinction.

Objective: Assess and compare the accuracy of the current AJCC TNM staging system among a large population-based cohort with SCC of the tonsil/BOT vs. other oropharyngeal subsites.

Study Design: Retrospective analysis of population-based data

Methods: Patients with oropharyngeal (OP) SCC were identified using the Surveillance Epidemiology and End Results database. Patients were classified according to the 6th edition AJCC TNM system, and also by primary site as follows: 1.) Tonsil/BOT(n=14,151), and 2.) Other oropharynx (including soft palate, uvula, and oropharyngeal walls n=1,437). The Kaplan-Meier method was used to estimate 5-year disease-specific survival (DSS) in each AJCC TNM classification group. Analyses were then stratified according to primary site subgroups.

Results: Patients with tonsil/BOT SCC were more likely to be younger white males with lower-T stage, and higher N- and overall-stage disease (p<0.001). There was a predominance of Stage IV disease in both groups, especially tonsil/BOT SCC (76% in tonsil/BOT and 65% in other OP subsites, p<0.001).

Within the cohort as a whole, five-year DSS was nearly equal in AJCC Stage II and III OP SCC (Fig1). Although DSS was well-discriminated according to T and M classifications, discrimination according to N classification was poor and not concordant between the 2 primary site subgroups. Patients with N2a SCC of the tonsil/BOT had significantly better DSS vs. those with N0/N1 disease (Fig2).

Conclusion: The absence of survival discrimination in stage II/III disease, and the skewed distribution of stage VI disease are suboptimal aspects of the current stage classification system for OP SCC. The current AJCC classification system also appears to be inadequate for staging tonsil/BOT tumors, especially regarding N stage. Unilateral nodal metastasis does not appear to uniformly denote a poor prognosis in OP SCC.

 

Fig 1:

Fig 2: