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 uses several clinicopathologic staging system tools, yet under- and overtreatment 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 5 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 risk (P < .0001) in a validation cohort (n = 572), with >95% negative predictive value 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 local recurrence risk more than individual clinicopathologic factors. LIMITATIONS: Retrospective study. CONCLUSIONS: i40-GEP accurately stratifies metastatic and local recurrence risk in patients with high-risk cutaneous squamous cell carcinoma, leading to improved clinical decision-making. Class 2B i40-GEP identifies patients most likely to benefit from ART.