Study Data from Castle Biosciences’ Collaboration with the National Cancer Institute’s SEER Program Registries Published in JCO Precision Oncology

Data shows testing with DecisionDx®-Melanoma provided significant prognostic information regarding survival outcomes

Castle Biosciences, Inc. (Nasdaq: CSTL), a company improving health through innovative tests that guide patient care, today announced the publication of a study in JCO Precision Oncology¹ in which DecisionDx®-Melanoma provided significant, independent risk stratification of patients with cutaneous melanoma (CM), beyond American Joint Committee on Cancer Eighth Edition (AJCC8) stage, which may help inform more personalized patient management decisions. Additionally, data from the study shows that testing with DecisionDx-Melanoma was associated with lower melanoma-specific and overall mortality relative to untested patients. The study can be found here.

“Management decisions for melanoma patients, such as referrals for sentinel lymph node biopsy or frequency and intensity of surveillance, are guided by a patient’s risk of disease recurrence or metastasis, and improvements in the accuracy of risk prediction can inform these decisions,” said Matthew Goldberg, M.D., F.A.A.D., board-certified dermatologist and dermatopathologist, and senior vice president, medical, of Castle Biosciences. “The independent risk-stratification provided by DecisionDx-Melanoma has already been demonstrated in numerous retrospective and prospective studies. This large study of real-world, unselected, clinically tested patients who received our test as part of their ongoing melanoma care further supports these findings.

“The statistically significant risk stratification for survival between patients who received a Class 1A test result (lowest risk of metastasis) and those with a Class 2B test result (highest risk of metastasis) highlights the value that testing with DecisionDx-Melanoma can bring to personalizing patient care decisions when interpreted in the context of the extensive, published clinical utility data for DecisionDx-Melanoma, including the recently published study from Dhillon et al.”²

In the study, to assess the effect of the DecisionDx-Melanoma test on survival outcomes, a group of tested patients (n=3,258) was matched to a group of patients who did not receive DecisionDx-Melanoma test results as part of their clinical care (n=9,774); the matching was performed using propensity score matching with three untested patients for each tested patient and was based on 11 clinicopathologic and socioeconomic variables.

Key findings of the study include:

• DecisionDx-Melanoma independently risk-stratified patients according to their risk of dying from melanoma, consistent with previously published retrospective and prospective studies.
• DecisionDx-Melanoma was an independent predictor of patient outcomes; a Class 2B (high risk) DecisionDx-Melanoma test result was an independent predictor of melanoma-specific survival (HR= 7.00, 95% CI 2.70-18.00) and overall survival (HR= 2.39, 95% CI 1.54-3.70). Additionally, a Class 2B result conferred the highest risk of all clinicopathologic factors included in multivariable analyses that included ulceration status, Breslow thickness and nodal status, the three risk factors used in the AJCC8 staging system.
• DecisionDx-Melanoma testing was associated with 29% lower melanoma-specific mortality (HR=0.71, 95% CI 0.53-0.94) and 17% lower overall mortality (HR=0.83, 95% CI 0.70-0.99) relative to patients who did not receive DecisionDx-Melanoma testing.

“We believe that DecisionDx-Melanoma will be a practice-changing test, providing personalized information based on the genomic profile of a patient’s tumor that can help guide more informed and risk-aligned patient care decisions,” said Derek Maetzold, president and chief executive officer of Castle Biosciences. “We are looking forward to continuing our collaboration with the NCI SEER Program’s Registries to provide DecisionDx Melanoma data to the SEER registries as part of public health reporting to further advance research and patient care.”

About DecisionDx®-Melanoma

DecisionDx-Melanoma is a gene expression profile risk stratification test. It is designed to inform two clinical questions in the management of cutaneous melanoma: a patient’s individual risk of sentinel lymph node (SLN) positivity and a patient's personal risk of melanoma recurrence and/or metastasis. By integrating tumor biology with clinical and pathologic factors using a validated proprietary algorithm, DecisionDx-Melanoma is designed to provide a comprehensive and clinically actionable result to guide risk-aligned patient care. DecisionDx-Melanoma has been shown to be associated with improved patient survival and has been studied in more than 10,000 patient samples. DecisionDx-Melanoma’s clinical value is supported by more than 40 peer-reviewed and published studies, providing confidence in disease management plans that incorporate the test’s results. Through March 31, 2023, DecisionDx-Melanoma has been ordered more than 128,000 times for patients diagnosed 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 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: (i) the potential of DecisionDx-Melanoma to provide significant prognostic information regarding survival outcomes which may allow for more personalized patient care, guide and inform management decisions for melanoma patients through risk prediction, and bring value to personalizing patient care decisions; and (ii) our belief that DecisionDx-Melanoma will be a practice-changing test, providing personalized information based on the genomic profile of a patient’s tumor that can help guide more informed and risk-aligned patient care decisions. The words “believe,” “can,” “may,” “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 shown in this study, including with respect to the discussion of DecisionDx-Melanoma 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 three months 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. Bailey C, Martin B, Petkov V, et al. 31-Gene Expression Profile Testing in Cutaneous Melanoma and Survival Outcomes in a Population-Based Analysis: A SEER Collaboration. JCO Precis. Oncol. 2023; 7. DOI: 10.1200/PO.23.00044
2. Dhillon S, Duarte-Bateman D, Fowler G, et al. Routine imaging guided by a 31-gene expression profile assay results in earlier detection of melanoma with decreased metastatic tumor burden compared to patients without surveillance imaging studies. Arch Dermatol Res. 2023. https://doi.org/10.1007/s00403-023-02613-6

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