Study Finds DecisionDx®-Melanoma Significantly Improves the Risk Stratification of Patients with Stage I Melanoma Compared to American Joint Committee on Cancer 8th Edition Staging

Study results, which include 5,651 patients in the National Cancer Institute’s Surveillance, Epidemiology and End Results (SEER) Program Registries, support the use of DecisionDx-Melanoma in stage I melanoma to help inform clinical decision-making

Castle Biosciences, Inc. (Nasdaq: CSTL), a company improving health through innovative tests that guide patient care, today announced the publication of a study in Cancers¹ demonstrating that DecisionDx-Melanoma provided significantly better risk stratification than American Joint Committee on Cancer 8th Edition (AJCC8) staging in patients with stage I cutaneous melanoma (CM). This study reports the results of two large stage I cohorts, including 5,651 patients from the National Cancer Institute’s SEER Program Registries (analyzing survival) and 1,261 patients from a combined cohort (analyzing recurrence and survival), and suggests that incorporating the DecisionDx-Melanoma test into clinical practice may help clinicians and patients obtain more precise information about a patient’s prognosis to inform more personalized, risk-aligned treatment and surveillance management plans.

“Relying on staging alone to determine a melanoma patient’s prognosis misses patients with aggressive tumor biology who may be at higher risk of recurrence, metastasis or death from their disease,” said Sebastian Podlipnik, M.D., Ph.D., lead study author and dermatologist at the Hospital Clínic de Barcelona, Universitat de Barcelona, in Spain. “As supported by the data in this study, incorporating DecisionDx-Melanoma test results into clinical decision-making can help identify which patients with lower stage tumors may be at higher risk of disease progression and could benefit from more aggressive follow-up schedules and treatment plans to identify recurrence earlier when it has generally been shown to have better treatment outcomes.”

Traditionally, treatment pathways for CM have been based upon clinicopathologic AJCC8 staging, which provides population-based risk of progression estimates. Stage I CM tumors are considered low risk; however, since stage I encompasses a large group of patients diagnosed, many melanoma-specific deaths are seen in patients initially diagnosed with stage I disease. Thus, there is a clinical gap in the low-risk treatment pathway for stage I patients. DecisionDx-Melanoma was developed and validated to provide a tumor-specific risk of recurrence, independent of the current risk factors used in AJCC8 staging, specifically tumor thickness and ulceration. The test classifies patients as having a low risk (Class 1A), intermediate risk (Class 1B/2A) or high risk (Class 2B) of tumor recurrence, metastasis and melanoma-specific mortality based on the patient’s tumor biology. As a result of this risk-stratification information, DecisionDx-Melanoma is used clinically to help inform patient-specific treatment pathway decisions.

The new study in Cancers provides further information that DecisionDx-Melanoma testing could enable more precise risk stratification in stage I melanomas than provided by traditional staging to better inform risk-appropriate clinical management. This multi-center study analyzed data from nearly 7,000 patients with stage I CM to assess their five-year recurrence-free survival (RFS) and melanoma-specific survival (MSS) using the DecisionDx-Melanoma test. There were two cohorts of patients: a pooled cohort from previous studies (combined cohort, n=1,261) and a second, large, real-world cohort of unselected patients who received the DecisionDx-Melanoma test as part of their clinical care (patients diagnosed with CM between 2013–2018 who were linked to outcomes data from the National Cancer Institute’s SEER Program registries, n=5,651). The combined cohort was evaluated for RFS and MSS, and the SEER cohort was evaluated for MSS.

In both cohorts, DecisionDx-Melanoma provided greater separation between patients with high- and low-risk test results than seen between AJCC8 stage IA and IB, demonstrating the ability of the test to provide improved risk stratification over staging.

Combined cohort

SEER cohort

In the combined cohort, multivariable analysis showed that a DecisionDx-Melanoma Class 2B test result was the strongest predictor of recurrence in stage I CM (HR = 5.16, p < 0.001); similarly, in the SEER cohort, multivariable analysis indicated that a high-risk test result was the only significant predictor of melanoma-specific mortality in stage I patients (HR = 9.23, p < 0.001).

The data in this study support the use of DecisionDx-Melanoma to help guide improved, risk-aligned care in patients considered low risk by staging (i.e., patients with stage I CM tumors) but who have aggressive molecular tumor biology and may be missed using only staging criteria for prognosis.

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 50 peer-reviewed and published studies, providing confidence in disease management plans that incorporate the test’s results. Through Sept. 30, 2023, DecisionDx-Melanoma has been ordered more than 146,000 times for patients diagnosed with cutaneous melanoma.

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

DecisionDx-Melanoma, DecisionDx-CMSeq, DecisionDx-SCC, MyPath Melanoma, TissueCypher, IDgenetix, DecisionDx-UM, DecisionDx-PRAME and DecisionDx-UMSeq 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 ability of DecisionDx-Melanoma to (i) provide significantly better risk stratification than AJCC8 staging in patients with stage I CM and (ii) help clinicians and patients obtain more precise information about a patient’s risk of disease progression to inform more personalized, risk-aligned treatment and surveillance management plans. The words “believe,” “can,” “potential,” “will” 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-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 quarter ended Sept. 30, 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. Podlipnik S, Martin BJ, Morgan-Linnell SK et al. The 31-gene expression profile test outperforms AJCC in stratifying risk of recurrence in patients with stage I cutaneous melanoma. Cancers. 2024;16(2):287. https://doi.org/10.3390/cancers16020287

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