Implications for clinical staging of metastatic cutaneous squamous carcinoma of the head and neck based on a multicenter study of treatment outcomes

BACKGROUND. Cutaneous squamous cell carcinoma (SCC) of the head and neck is a common cancer that has the potential to metastasize to lymph nodes in the parotid gland and neck. Previous studies have highlighted limitations with the current TNM staging system for metastatic skin carcinoma. The aim of this study was to test a new staging system that may provide better discrimination between patient groups. METHODS. A retrospective multicenter study was conducted on 322 patients from three Australian and three North American institutions. All had metastatic cutaneous SCC involving the parotid gland and/or neck and all were treated for cure with a minimum followup time of 2 years. These patients were restaged using a newly proposed system that separated parotid disease (P stage) from neck disease (N stage) and included subgroups of P and N stage. Metastases involved the parotid in 260 patients (149 P1; 78 P2; 33 P3) and 43 of these had clinical neck disease also (22 N1; 21 N2). Neck metastases alone occurred in 62 patients (26 N1; 36 N2). Ninety percent of patients were treated Surgically and 267 of 322 received radiotherapy. RESULTS. Neck nodes were pathologically involved in 32% of patients with parotid metastases. Disease recurred in 105 (33%) of the 322 patients, involving the parotid in 42, neck in 33, and distant sites in 30. Parotid recurrence did not vary significantly with P stage. Disease-specific survival was 74% at 5 years. Survival was significantly worse for patients with advanced P stage: 69% survival at 5 years compared with 82% for those with early P stage (P = 0.02) and for those with both parotid and neck node involvement pathologically: 61% survival compared with 79% for those with parotid disease alone (P = 0.027). Both univariate and multivariate analysis confirmed these findings. Clinical neck involvement among patients with parotid metastases did not significantly worsen survival (P = 0.1). CONCLUSIONS. This study, which included a mixed cohort of patients from six different institutions, provides further information about the clinical behavior of metastatic cutaneous SCC of the head and neck. The hypothesis that separation of parotid and neck disease in a new staging system is supported by the results. The benefit of having subgroups of P and N stage is uncertain, but it is likely to identify patients with unfavorable characteristics that may benefit from further research.