Late-Breaking Data Presented at the 2023 AAD Annual Meeting Demonstrates Improved Accuracy of DecisionDx®-SCC in Predicting Metastatic Risk Over Traditional Staging Systems in Independent, Multi-Center Cohort Study

FRIENDSWOOD, Texas–(BUSINESS WIRE)–Castle Biosciences, Inc. (Nasdaq: CSTL), a company improving health through innovative tests that guide patient care, today shared new performance data from a novel, multi-center, independent cohort demonstrating how the independent risk-stratification of DecisionDx®-SCC (the Company’s 40-gene expression profile (GEP) test) can significantly improve metastatic risk predictions by complementing current staging systems (AJCC8¹ and BWH²). Additionally, consistent with previous studies,^3,4 DecisionDx-SCC independently and significantly stratified a novel cohort according to patients’ biologic metastatic risk (p<0.0001).

Details from the study will be shared by Ashley Wysong, M.D., M.S., F.A.A.D., William W. Bruce, M.D. Distinguished Chair of Dermatology and Founding Chair of the Department of Dermatology at the University of Nebraska Medical Center, in a late-breaking oral presentation later today during the 2023 American Academy of Dermatology (AAD) Annual Meeting.

• Presentation title: The 40-gene expression profile (40-GEP) continues to demonstrate independent metastatic risk stratification and improved accuracy in risk assessment in a novel cohort of cutaneous squamous cell carcinoma (cSCC) patients with one or more risk factors
• Date: Today, Saturday, March 18
• Session: S042 – Late-Breaking Research: Session 2
• Time: 3:40-3:50 p.m. Central time
• Location: New Orleans Ernest N. Morial Convention Center Theater B

“With the deaths from cSCC now expected to exceed those from melanoma, there is a greater need for tools that complement traditional staging systems with independent information regarding a patient’s biologic risk of metastasis,” said Wysong. “The results from this study demonstrate that gene expression profiling can significantly improve metastatic risk predictions over those based on staging alone, supporting the ability of the 40-GEP test to enhance the care of high-risk cSCC patients by guiding risk-adjusted patient care decisions.”

This study analyzed the performance of the DecisionDx-SCC test in a novel, independent performance cohort of 534 patients with primary cSCC and one or more risk factors from 45 contributing centers. The data from the study consistently demonstrated the performance of DecisionDx-SCC to classify risk for metastasis in cSCC patients with one or more risk factors (p<0.0001). Multivariate models showed that the metastatic risk prediction of AJCC8 and BWH staging systems were significantly improved when DecisionDx-SCC test results were included (likelihood ratio of AJCC8 staging alone=62.0 vs. AJCC8 + DecisionDx-SCC=78.2 (p=0.0003); likelihood ratio of BWH staging alone=70.0 vs. BWH + DecisionDx-SCC=83.6 (p=0.001)). Overall, the study data further support that DecisionDx-SCC independently predicts metastatic risk for patients with cSCC and can complement clinicopathologic staging systems and improve risk predictions based on staging alone to support risk-aligned patient management decisions.

About DecisionDx®-SCC

DecisionDx-SCC is a 40-gene expression profile test that uses an individual patient’s tumor biology to predict individual risk of cutaneous squamous cell carcinoma metastasis for patients with one or more risk factors. The test result, in which patients are stratified into a Class 1 (low), Class 2A (moderate) or Class 2B (high) risk category, predicts individual metastatic risk to inform risk-appropriate management.

Peer-reviewed publications have demonstrated that DecisionDx-SCC is an independent predictor of metastatic risk and that integrating DecisionDx-SCC with current prognostic methods can add positive predictive value to clinician decisions regarding staging and management.

More information about the disease and test can be found at www.CastleTestInfo.com.

About Castle Biosciences

Castle Biosciences (Nasdaq: CSTL) is a leading diagnostics company improving health through innovative tests that guide patient care. The Company aims to transform disease management by keeping people first: patients, clinicians, employees and investors.

Castle’s current portfolio consists of tests for skin cancers, uveal melanoma, Barrett’s esophagus and mental health conditions. Additionally, the Company has active research and development programs for tests in other diseases with high clinical need, including its test in development to predict systemic therapy response in patients with moderate-to-severe psoriasis, atopic dermatitis and related conditions. To learn more, please visit www.CastleBiosciences.com and connect with us on LinkedIn, Facebook, Twitter and Instagram.

DecisionDx-Melanoma, DecisionDx-CMSeq, DecisionDx-SCC, MyPath Melanoma, DiffDx-Melanoma, DecisionDx-UM, DecisionDx-PRAME, DecisionDx-UMSeq, TissueCypher and IDgenetix are trademarks of Castle Biosciences, Inc.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended, which are subject to the “safe harbor” created by those sections. These forward-looking statements include, but are not limited to, statements concerning: the potential of DecisionDx-SCC and GEP testing to significantly improve metastatic risk predictions over those based on staging alone and support risk-aligned patient management decisions when combined with clinicopathologic staging. The words “can,” “potential” and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. We may not actually achieve the plans, intentions or expectations disclosed in our forward-looking statements, and you should not place undue reliance on our forward-looking statements. Actual results or events could differ materially from the plans, intentions and expectations disclosed in the forward-looking statements that we make. These forward-looking statements involve risks and uncertainties that could cause our actual results to differ materially from those in the forward-looking statements, including, without limitation: subsequent study or trial results and findings may contradict earlier study or trial results and findings or may not support the results obtained in this study, including with respect to the discussion of DecisionDx-SCC in this press release; actual application of our tests may not provide the aforementioned benefits to patients; and the risks set forth under the heading “Risk Factors” in our Annual Report on Form 10-K for the year ended December 31, 2022, and in our other filings with the SEC. The forward-looking statements are applicable only as of the date on which they are made, and we do not assume any obligation to update any forward-looking statements, except as may be required by law.

1. AJCC8: American Joint Committee on Cancer 8th edition staging system
2. BWH: Brigham and Women’s Hospital staging system
3. Wysong, A, Newman J, Covington K, et al. Validation of a 40-gene expression profile test to predict metastatic risk in localized high-risk cutaneous squamous cell carcinoma. JAAD. 2021;84(2):361-368. doi: https://www.jaad.org/article/S0190-9622(20)30704-0/fulltext
4. Ibrahim S, Kasprzak J, Hall M, et al. Enhanced metastatic risk assessment in cutaneous squamous cell carcinoma with the 40-gene expression profile test. Future Oncol. 2021;18(7):833-847. doi: https://doi.org/10.2217/fon-2021-1277