Validation of the integrated 40-gene expression profile (i40-GEP) which provides prognostic and adjuvant radiation benefit for high-risk cutaneous squamous cell carcinoma.

BACKGROUND: Risk assessment in high-risk cutaneous squamous cell carcinoma (HRcSCC) uses several clinicopathologic staging system tools, yet under- and over-treatment often occur. Integration of tumor biology as an independent predictor via gene expression profile (GEP) may improve risk stratification and tailor adjuvant care. OBJECTIVE: Integrate clinicopathologic risk factors with 40-GEP testing to refine risk stratification. METHODS: Integrated 40-GEP (i40-GEP) combines optimized nested predictive models and five clinicopathologic features (immunosuppression, location, differentiation, tumor diameter, and perineural invasion) with the validated 40-GEP, and reports results: Class 1A (Low Risk), Class 1B (Moderate Risk), Class 2A (High Risk), and Class 2B (Highest Risk). RESULTS: i40-GEP significantly stratifies metastatic and local recurrence (LR) risk (p<0.001) in a validation cohort (n=572), with >95% NPV for Class 1A across National Comprehensive Cancer Network subsets. The i40-GEP identified 12.9% of patients as Class 2B, with the lowest 3-year metastasis-free survival (66.2%) and a demonstrated benefit from adjuvant radiation treatment (ART). Multivariable analysis showed i40-GEP results significantly predict metastatic and LR risk more than individual clinicopathologic factors. LIMITATIONS: Retrospective study. CONCLUSIONS: I40-GEP accurately stratifies metastatic and LR risk in patients with HRcSCC, leading to improved clinical decision-making. Class 2B i40-GEP identifies patients most likely to benefit from ART.