Prognostic importance of radiologic extranodal extension in HPV-positive oropharyngeal carcinoma and its potential role in refining TNM-8 cN-classification

Abstract Purpose This study examines outcome heterogeneity and potential to refine the TNM-8 cN-classification using radiologic extranodal extension (rENE) in a contemporary HPV-positive (HPV+) oropharyngeal carcinoma (OPC) cohort. Methods All HPV+ OPC treated with definitive IMRT from 2010-2015 were included. Pre-treatment CT/MR of cN+ cases were reviewed by a head-neck radiologist for rENE. Overall survival (OS) and disease-free survival (DFS) were compared between rENE-positive (rENE+) vs rENE-negative (rENE−). Multivariable analysis (MVA) for OS confirmed the prognostic value of rENE. Refined cN-classifications for new TNM staging proposals were evaluated against TNM-8 using established criteria. Results A total of 517 cN+ (rENE+: 97; rENE−: 420) and 41 cN0 cases were identified. The rENE+ proportion increased with rising N-category (N1/N2/N3: 11%/19%/84%, p  Conclusion This study confirms that rENE is prognostically important and facilitates understanding of known outcome heterogeneity within TNM-8 in HPV+ OPC patients. rENE is a promising parameter to refine the TNM-8 cN-classifications.