A new American Joint Committee on Cancer staging system for cutaneous squamous cell carcinoma: Creation and rationale for inclusion of tumor (T) characteristics

Background: The incidence of cutaneous squamous cell carcinoma (cSCC) is increasing. Although most patients achieve complete remission with surgical treatment, those with advanced disease have a poor prognosis. The American Joint Committee on Cancer (AJCC) is responsible for the staging criteria for all cancers. For the past 20 years, the AJCC cancer staging manual has grouped all nonmelanoma skin cancers, including cSCC, together for the purposes of staging. However, based on new evidence, the AJCC has determined that cSCC should have a separate staging system in the 7th edition AJCC staging manual. Objective: We sought to present the rationale for and characteristics of the new AJCC staging system specific to cSCC tumor characteristics (T). Methods: The Nonmelanoma Skin Cancer Task Force of AJCC reviewed relevant data and reached expert consensus in creating the 7th edition AJCC staging system for cSCC. Emphasis was placed on prospectively accumulated data and multivariate analyses. Concordance with head and neck cancer staging system was also achieved. Results: A new AJCC cSCC T classification is presented. The T classification is determined by tumor diameter, invasion into cranial bone, and high-risk features, including anatomic location, tumor thickness and level, differentiation, and perineural invasion. Limitations: The data available for analysis are still suboptimal, with limited prospective outcomes trials and few multivariate analyses. Conclusions: The new AJCC staging system for cSCC incorporates tumor-specific (T) staging features and will encourage coordinated, consistent collection of data that will be the basis of improved prognostic systems in the future.