Framework Incorporating DecisionDx®-SCC Test Results into Clinical Decision-Making for Patients with High-Risk Cutaneous Squamous Cell Carcinoma Published in Clinical, Cosmetic and Investigational Dermatology

Treatment algorithm can assist clinicians in tailoring their care for patients with high-risk cutaneous squamous cell carcinoma (cSCC) based on individual patient’s unique tumor biology, while adhering to guideline recommendations

Castle Biosciences, Inc. (Nasdaq: CSTL), a company improving health through innovative tests that guide patient care, today announced the publication of a paper in Clinical, Cosmetic and Investigational Dermatology highlighting a clinician-derived, real-world algorithm that provides a framework to incorporate DecisionDx®-SCC test results into clinical practice within National Comprehensive Cancer Network (NCCN) guideline recommendations.¹ This framework for stratifying patients with advanced cSCC includes a treatment algorithm that demonstrates how use of DecisionDx-SCC test results can assist clinicians in identifying personalized, risk-aligned treatment pathway improvements for patients with high-risk cSCC, based on the patient’s tumor biology, which may help improve their disease outcome.

“While current guidelines and staging frameworks for cSCC provide guidance for stratifying patients based on their risk of metastasis, the recommendations can be challenging to implement as they are based on a broad set of clinicopathologic risk factors,” said first author Gaurav Singh, M.D., M.P.H., F.A.A.D., board-certified dermatologist and fellowship-trained Mohs surgeon in Milwaukee. “The algorithm that we developed is not meant to challenge these established guidelines. Rather, it is designed to enhance existing risk-stratification approaches by integrating a patient’s tumor biology into the decision-making process through the use of DecisionDx-SCC test results and providing options for clinicians to consider when deciding future steps in the care of each patient.”

The DecisionDx-SCC test has been validated to independently identify cSCC patients who have tumors with high metastatic potential. In the study, three private-practice Mohs surgeons, who routinely use the test to risk-stratify their high-risk cSCC patients, merged their management approaches for three real-world, high-risk cSCC patients into a singular algorithm that provides a framework for incorporating each of the test’s three potential results into current NCCN guidelines. This algorithm adds greater specificity to the broad guidelines for the treatment of high-risk cSCC patients, including surveillance imaging, sentinel lymph node biopsy, adjuvant radiation therapy and clinical follow-up, which frequently result in disparities in clinical practice and management, and provide guidance on how to use each based on the patient’s DecisionDx-SCC test results.

The three patient cases discussed in the paper provide support for the clinical utility of DecisionDx-SCC to provide a more definitive, risk-aligned use of these treatment modalities in an effort to improve patient care and overall health outcomes. In all three cases presented in the study, use of the algorithm incorporating DecisionDx-SCC test results led to no evidence of disease recurrence or metastasis post-treatment, based on the timing described in the study. The study findings support the use of DecisionDx-SCC test results within established guidelines to enable personalized, risk-aligned management of high-risk cSCC patients and the allocation of healthcare resources to patients at the highest risk of a poor outcome.

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, 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 test results to assist clinicians in (i) tailoring their care for patients with high-risk cSCC based on the patient’s unique tumor biology, while adhering to guideline recommendations, and (ii) identifying personalized, risk-aligned treatment pathway improvements for patients with high-risk cSCC, based on the patient’s tumor biology, which may help improve their disease outcome. The words “can,” “may” 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 shown 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 Quarterly Report on Form 10-Q for the quarter ended March 31, 2023, 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. Singh G, Tolkachjov SN, Farberg AS. Incorporation of the 40-Gene Expression Profile (40-GEP) Test to Improve Treatment Decisions in High-Risk Cutaneous Squamous Cell Carcinoma (cSCC) Patients: Case Series and Algorithm. Clin Cosmet Investig Dermatol. 2023;16:925-935. https://doi.org/10.2147/CCID.S403330

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