Disease Progression in Cutaneous Squamous Cell Carcinoma Patients With Satellitosis and In-transit Metastasis

Satellitosis/in-transit metastasis (S-ITM) has prognostic value in melanoma and Merkel cell carcinoma, but is not incorporated into cutaneous squamous cell carcinoma (cSCC) staging.

From our IRB-approved registry, patients with high-risk cSCC, including patients with S-ITM, were identified. Univariate (UVA) and multivariate (MVA) analyses were performed to compare disease progression (DP) and overall survival (OS). Cumulative incidence of DP and OS analyses were performed using Fine-Gray and Kaplan-Meier methods, respectively.

A total of 18 S-ITM subjects were compared to 247 high risk subjects including T3N0 (n=143), N1-N3 without extranodal extension (ENE) (n=56), N1-N3 with ENE (n=26) and M1 disease (n=22). Median follow up was 16.5 months. Three-year rates of DP were 22% for T3N0, 42% for S-ITM, 48% for T4 bone invasion, 50% for N1-N3 without extranodal extension (ENE), 53% for N1-N3 with ENE, and 66% for M1. Patients with S-ITM did not experience significantly worse DP compared to those with T3N0 (HR=1.96, 95%CI=0.8-4.9; p=0.14).

Cutaneous SCC patients with S-ITM experienced outcomes similar to locally advanced non-metastatic cSCC patients. Larger studies are needed to guide incorporation into staging systems.