Castle Biosciences, Inc. announced new data showing that DecisionDx-SCC can independently risk-stratify patients with cutaneous squamous cell carcinoma (SCC) and one or more risk factors according to their biologic risk of metastasis, consistent with findings in previous development and validation studies. The poster was presented at the 2022 American College of Mohs Surgery (ACMS) Annual Meeting. DecisionDx-SCC is Castle's prognostic 40-gene expression profile (GEP) test designed to use a patient's tumor biology to predict individual risk of metastasis for patients diagnosed with SCC who have one or more high-risk factors.

The test stratifies patients into one of three classes based on their biologic risk of metastasis: Class 1 (low risk), Class 2A (moderate risk) or Class 2B (high risk). The poster, titled “Performance of the prognostic 40-gene expression profile (40-GEP) test for high-risk cutaneous squamous cell carcinoma (cSCC) in a second independent cohort,” highlights data from a second, independent, multi-center study of high-risk SCC patients, consisting of 598 novel patient samples from 43 contributing centers. The poster can be viewed here.

With the cohort of patients in this study, combined with the cohort of patients from the first validation study (n=420), the ability of DecisionDx-SCC to independently stratify risk has been confirmed in a total of 1,018 patients. Kaplan-Meier analysis showed a statistically significant difference in metastasis-free survival (MFS) rates between DecisionDx-SCC Class 1, Class 2A and Class 2B results (p<0.0001, log-rank), demonstrating the ability of the test to risk-stratify patients according to their biologic metastatic risk. As demonstrated by univariate Cox regression analysis, DecisionDx-SCC Class 2A, Class 2B, traditional high-risk clinicopathologic risk factors, American Joint Committee on Cancer Eighth Edition (AJCC8) T3/T4 stages and Brigham and Women's Hospital (BWH) T2b/T3 stages were all statistically associated with metastatic risk.

A DecisionDx-SCC Class 2B result had the high hazard ratio, 10.71, which was the strongest predictor of metastasis among the analyses. Further, multivariate Cox regression analysis demonstrated that DecisionDx-SCC independently and significantly contributed to risk stratification of patients when combined with traditional high-risk clinicopathologic factors (p<0.05 for Class 2A and 2B), BWH (p<0.001 for Class 2A and p<0.002 for Class 2B) or AJCC8 (p<0.001 for Class 2A and 2B) staging. This reinforces that the test's results provide risk-stratification value on their own and can add clinical value when used as a complement to other risk-prediction systems. Overall, the study data confirm what previous development and validation studies1,2 have substantiated: DecisionDx-SCC can accurately classify risk for metastasis in SCC patients with one or more risk factors and provides significant prognostic information independent from current risk prediction methods.

Additionally, the study data further support the use of DecisionDx-SCC test results in combination with other risk-assessment and staging systems to guide more refined and risk-aligned patient care.