The American Joint Committee on Cancer staging for metastatic head and neck cutaneous squamous cell carcinoma: A multi-institutional study of within-stage heterogeneity and impact on prognostic performance.

BACKGROUND The American Joint Committee on Cancer (AJCC) staging for head and neck cutaneous squamous cell carcinoma (HNcSCC) stratifies risk poorly. We hypothesized that this results from prognostic heterogeneity within N and TNM groups. METHODS Retrospective analysis of disease-specific survival (DSS) in a multicenter study of 1146 patients with nodal metastases from HNcSCC. RESULTS The majority of patients were classified as pN2a or pN3b (83.1%) and TNM stage IV (90.6%). On multivariate analysis, there was statistically significant prognostic heterogeneity within these groups based on the number and size of nodal metastases, immunosuppression, and perineural invasion. When stage IV patients were categorized into low, moderate, and high-risk groups based on adverse features, there was wide variation in prognosis with 5-year DSS ranging from 90% to 60% (P < .001). CONCLUSIONS The AJCC staging system stratifies risk poorly in HNcSCC due to significant prognostic heterogeneity within pN2a, pN3b, and stage IV groups.