The 40-gene Expression Profile (40-GEP) Test Identifies Cutaneous Squamous Cell Carcinoma (cSCC) Patients at High Risk of Metastasis within Lower-Staged Tumors to Better Guide Treatment Decisions

Introduction- The development of metastases has a profound impact on cSCC patient survival. Lower-stage tumors are those that lack factors that portend higher risk for disease progression and therefore not typically considered for increased surveillance or treatment. However, up to one-third of all metastatic events have been reported for patients originally staged as T1. The 40-GEP test is validated to accurately classify risk for regional and/or distant metastasis in patients with primary cSCC with at least one high-risk factor. The current study investigated whether the 40-GEP test could independently improve identification of lower-staged tumors at increased risk of metastasis. Methods- In an IRB-approved, retrospective, multi-center study, primary tumor tissue and associated clinical data from patients with cSCC and one or more clinicopathologic risk factors (n=897) were collected. Within this overall cohort, lower Brigham and Women’s Hospital (BWH) T-staged samples (n=444 T1 and n=335 T2a) were evaluated by Kaplan-Meier survival analysis to determine metastasis-free survival (MFS) according to 40-GEP risk class (Class 1-low metastatic risk; Class 2A-higher risk; Class 2B-highest risk). Results- There was a total of 118 metastatic events in the overall cohort, of which 25% (29/118) and 38% (45/118) occurred in BWH T1 and T2a, respectively. BWH T1 tumors had an overall event rate of 6.5% (29/444), with T1/Class 2B tumors having a 5.1-fold increased event rate of 33.3%. BWH T2a tumors had an overall event rate of 13.4% (45/335), with T2a/Class 2B tumors having a 2.7-fold increased event rate of 36.4%. Stratification by the 40-GEP test resulted in significantly different metastasis rates across all three 40-GEP classes within both the T1 and T2a subsets (log-rank tests, p<0.0001 each subset). Conclusion- Within a cohort of cSCC patients considered lower risk by current staging alone, the 40-GEP identified patients with a substantial increase in metastatic risk. The observed rates of metastasis over 10% and 20% are clinically actionable for nodal staging or postoperative adjuvant radiation, respectively. Combining clinicopathologic risk assessment with individual biologic risk, as provided by the 40-GEP test, improves the accuracy of risk assessment used clinically as the basis of treatment decisions.