Castle Biosciences Presents New Data Demonstrating DecisionDx®-SCC Complements Current Risk Assessment Methods in Patients with Cutaneous Squamous Cell Carcinoma of the Head and Neck

Data Presented at American Head & Neck Society (AHNS) 10th International Conference on Head and Neck Cancer

Castle Biosciences, Inc. (Nasdaq: CSTL), a dermatologic diagnostics company providing personalized genomic information to inform treatment decisions, today announced a podium presentation on its DecisionDx®-SCC test at the American Head & Neck Society (AHNS) 10th International Conference on Head and Neck Cancer, being held July 22-25, 2021.

DecisionDx-SCC is Castle’s prognostic 40-gene expression profile (GEP) test for patients diagnosed with high-risk cutaneous squamous cell carcinoma (SCC), designed to use a patient’s tumor biology to predict individual risk of metastasis for patients with SCC and one or more risk factors.

“Comparison of the 40-Gene Expression Profile Test with Clinicopathologic Risk Factor-Based Assessment to Improve Metastasis Risk Assessment in Cutaneous Squamous Cell Carcinoma of the Head and Neck” will be presented by Jason G. Newman, M.D., University of Pennsylvania Health System, Philadelphia, on July 23 at 3:30 p.m.-4:20 p.m. Central time.

“Study data demonstrate that DecisionDx-SCC is a valuable complement to traditional and trusted risk assessment systems, including the American Joint Committee on Cancer Eighth Edition (AJCC8) and Brigham and Women's Hospital (BWH) tumor (T) classification,” said Newman. “The data further demonstrate that Castle’s DecisionDx-SCC test can provide clinicians with additional information on a patient’s metastatic risk to help them make more informed choices about their treatment and follow-up care.”

Study methods and findings:

• Archival, primary tumor specimens and associated data from a cohort of 278 patients from 33 different clinical sites were included in the study; the patients had high-risk SCC located on the head or neck, and 54 patients (19.4%) developed regional and/or distant metastasis.
• All SCC tumor specimens were tested with DecisionDx-SCC and analyzed using Kaplan-Meier for metastasis-free survival (MFS) and Cox regression for risk of regional/distant metastasis.
• Patients who received a Class 1 (low biological risk), Class 2A (moderate biological risk) or Class 2B (high biological risk) DecisionDx-SCC result had significantly different three-year MFS rates (92.1%, 76.1% or 44.4%, respectively; p<0.0001, log-rank test) compared to the overall cohort MFS rate of 81.3%.
• Univariate Cox regression analysis demonstrated that the GEP test has significant, independent prognostic value. Multivariate Cox regression analysis demonstrated that the DecisionDx-SCC results compared to AJCC8 T staging was the most significant predictor of outcomes with a Hazard Ratio of 9.07 compared to AJCC8 at 2.88. Similar results were shown when the GEP test was compared with BWH T stages and individual clinicopathologic risk factors, such as tumor diameter, deep invasion, poor differentiation and perineural invasion.
• The specificity and positive predictive value (PPV) of a high-risk Class 2B DecisionDx-SCC result were improved relative to these metrics for high-stage AJCC8 (T3/T4) and BWH (T2b/T3), while maintaining a similar negative predictive value (NPV).
• Overall, the study demonstrated that DecisionDx-SCC offers significant, independent prognostic value for determining a patient’s individual risk of SCC metastasis, and that the test could be used to complement AJCC8 and BWH T staging and a patient’s clinicopathologic risk factor-based assessment.

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), 2A (moderate) or 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 test and disease can be found at www.CastleTestInfo.com.

About Castle Biosciences

Castle Biosciences (Nasdaq: CSTL) is a commercial-stage dermatologic diagnostics company focused on providing physicians and their patients with personalized, clinically actionable genomic information to make more accurate treatment decisions. The Company currently offers tests for patients with cutaneous melanoma (DecisionDx^®-Melanoma, DecisionDx^® -CMSeq), cutaneous squamous cell carcinoma (DecisionDx^®-SCC), suspicious pigmented lesions (myPath® Melanoma, DecisionDx^® DiffDx™-Melanoma,) and uveal melanoma (DecisionDx^®-UM, DecisionDx^®-PRAME and DecisionDx^®-UMSeq). For more information about Castle’s gene expression profile tests, visit www.CastleTestInfo.com.

Castle also has active research and development programs for tests in other dermatologic 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. Castle Biosciences is based in Friendswood, Texas (Houston), and has laboratory operations in Phoenix. Additionally, in May of 2021, Castle acquired the myPath Melanoma laboratory in Salt Lake City.

For more information, visit www.CastleBiosciences.com.

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

Forward-Looking Statements

The information in this press release contains forward-looking statements and information 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 DecisionDx-SCC’s ability to predict individual risk of metastasis for patients with SCC and one or more risk factors, complement to traditional risk assessment systems, including the AJCC8 and BWH T, and provide clinicians with additional information on a patient’s metastatic risk and help them make more informed choices about their treatment and follow-up care. The words “anticipates,” “believes,” “estimates,” “expects,” “intends,” “may,” “plans,” “projects,” “will,” “would” 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, the effects of the COVID-19 pandemic on our business and our efforts to address its impact on our business, subsequent study results and findings that contradict earlier study results and findings, DecisionDx-SCC’s ability to provide the aforementioned benefits to patients and the risks set forth in our Quarterly Report on Form 10-Q for the quarter ended March 31, 2021, 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.

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