Castle Biosciences Announces Prospective, Multi-Center Publication Demonstrating DecisionDx®-Melanoma as Significant, Independent Predictor of Patient Outcomes in Cutaneous Melanoma

Study published in JCO Precision Oncology

Castle Biosciences, Inc. (Nasdaq: CSTL), a skin cancer diagnostics company providing personalized genomic information to improve cancer treatment decisions, today announced the publication of prospective, multi-center long-term outcomes data in cutaneous melanoma as impacted by DecisionDx®-Melanoma. DecisionDx-Melanoma is Castle’s gene expression profile test that uses an individual patient’s tumor biology to predict risk of cutaneous melanoma metastasis or recurrence, as well as sentinel lymph node positivity, independent of traditional staging factors.

The article, titled “Long-term outcomes in a multicenter, prospective cohort evaluating the prognostic 31-gene expression profile for cutaneous melanoma,” was published in the peer-reviewed journal, JCO® Precision Oncology.

Study background:

The study’s key objective was to demonstrate the prognostic value of DecisionDx-Melanoma with long-term follow-up that extends the assessment time period for a previously studied cohort. The study achieved its primary objective and expanded upon prior results to show the ability of the test to accurately identifying recurrence risk of patients with American Joint Committee on Cancer (AJCC) 8^th Edition staging system early stage I-IIA disease.

Study results:

Consistent with previous prospective validation and performance studies, the DecisionDx-Melanoma test was significantly associated with the outcomes of recurrence-free (RFS), distant metastasis-free (DMFS) and overall survival (OS) in univariate analysis of patients diagnosed with stage I-III melanoma. The test’s result was also a significant, independent predictor of the same endpoints when compared to AJCC staging in multivariable analysis. Additionally, study authors conclude that combining DecisionDx-Melanoma test results with AJCC staging enhances sensitivity and negative predictive value over each approach alone, identifying those who may benefit from more or less intense follow-up. Further, accurate risk stratification by the DecisionDx-Melanoma test was demonstrated in the cohort of patients with stage I-IIA melanoma, a group that is currently recommended to receive low-intensity management but that contributes substantially to the number of patients who die from melanoma each year.

“The most impactful measures of appropriate melanoma management include survival time and the quality of that time post-diagnosis,” said first author Eddy Hsueh, M.D., surgical oncologist at St. Louis University, St. Louis, MO. “In this study, we demonstrated that DecisionDx-Melanoma results are significant predictors of real-world recurrence and metastasis rates, which suggests that the test can provide clinically actionable information when making cancer management decisions in early-stage melanoma.”

About DecisionDx-Melanoma

DecisionDx®-Melanoma is a gene expression profile test that uses an individual patient’s tumor biology to predict individual risk of cutaneous melanoma metastasis or recurrence, as well as sentinel lymph node positivity, independent of traditional staging factors, and has been studied in more than 5,700 patient samples. Using tissue from the primary melanoma, the test measures the expression of 31 genes. The test has been validated in four archival risk of recurrence studies of 901 patients and six prospective risk of recurrence studies including more than 1,600 patients. To predict likelihood of sentinel lymph node positivity, the Company utilizes its proprietary algorithm, i31-GEP, to produce an integrated test result. i31-GEP is an artificial intelligence-based neural network algorithm (independently validated in a cohort of 1,674 prospective, consecutively tested patients with T1-T4 cutaneous melanoma) that integrates the DecisionDx-Melanoma test result with the patient’s traditional clinicopathologic features. Impact on patient management plans for one of every two patients tested has been demonstrated in four multicenter and single-center studies including more than 560 patients. The consistent performance and accuracy demonstrated in these studies provides confidence in disease management plans that incorporate DecisionDx-Melanoma test results. Through December 31, 2020, DecisionDx-Melanoma has been ordered more than 68,920 times for use in patients with cutaneous melanoma.

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 cancer 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 (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. Castle Biosciences is based in Friendswood, Texas (Houston), and has laboratory operations in Phoenix, Arizona. For more information, visit www.CastleBiosciences.com.

DecisionDx-Melanoma, DecisionDx-CMSeq, DecisionDx-SCC, 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-Melanoma’s ability to accurately predict individual risk of cutaneous melanoma metastasis or recurrence, improve prognostic accuracy over sentinel lymph node biopsy results, add prognostic value to relevant clinicopathologic features, and provide clinically actionable information when making cancer management decisions in early-stage melanoma. 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, subsequent study results and findings that contradict earlier study results and findings, DecisionDx-Melanoma’s ability to provide the aforementioned benefits to patients and the risks set forth in our Annual Report on Form 10-K for the year ended December 31, 2020, 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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