Newly Published Study Establishes Evidence-Based Population for Clinical Use of DecisionDx-Melanoma in Patients With Thin Cutaneous Melanoma Tumors

Castle Biosciences, Inc., a skin cancer diagnostics company providing personalized genomic information to improve cancer treatment decisions, today announced the publication of a study that establishes an evidence-based population to guide appropriate use of the DecisionDx^®-Melanoma test in patients with thinner tumors. The study was published in the peer-reviewed journal SKIN: The Journal of Cutaneous Medicine.

Current best practice for the use of DecisionDx-Melanoma includes informing two key treatment plan decisions following a melanoma diagnosis. First, for most patients with cutaneous melanoma who are eligible for a sentinel lymph node biopsy (SLNB), DecisionDx-Melanoma can identify patients at low risk of positivity and inform the decision to undergo this surgical procedure. This can include patients with tumor thickness less than or equal to 2.0 mm with no minimum thickness criteria.

The second use for DecisionDx-Melanoma is designed to predict an individual’s risk of recurrence to help physicians determine an appropriate level of follow-up, imaging and referrals. Previously published validation studies have reported that the test can accurately determine risk of recurrence in patients with Stage I-III melanoma, including tumors with a thickness less than 1.0 mm. The purpose of this study was to determine whether an evidence-based thickness threshold can be established for this second use to further guide appropriate clinical use of the test in patients with thinner (1.0 mm or less) melanoma tumors.

Key Study Findings:

• An analysis of a large, multicenter dataset (n=1,479) that calculated event rates by tumor thickness and DecisionDx-Melanoma class result found a separation of recurrence rates between Class 1A (lowest risk) and Class 2B (highest risk) at a threshold of 0.3 mm.
• In a separate analysis of tumors ≤1.0 mm thick tested clinically (n=8,944) and at a large dermatopathology practice (n=437), tumors with a thickness between 0.3 mm and 1.0 mm showed a 10.8% and 15.7% non-Class 1A result, respectively, suggesting that there is a benefit of risk assessment for this portion of the thin tumor population.
• In two multicenter studies (n=403) that included 160 patients with tumors ≤1.0 mm, most patient management changes made following DecisionDx-Melanoma testing were recommended for those with a tumor thickness ≥0.3 mm.

These results suggest a minimum Breslow thickness of 0.3 mm as an appropriate population to use DecisionDx-Melanoma to guide decisions on follow-up for cutaneous melanoma patients. Based on a previously published validation study, the test can also be used to inform decisions on SLNB in most eligible patients with tumor thickness less than or equal to 2.0 mm (no minimum tumor thickness).

“Accurate risk assessment is especially important in patients with thinner melanomas because a substantial proportion of melanoma-specific deaths occur in patients initially diagnosed with thin melanomas,” commented study co-author Clay J. Cockerell, M.D., Cockerell Dermatopathology, Dallas, Texas. “These results establish an evidence-based population of patients with thin tumors who are appropriate for DecisionDx-Melanoma testing to inform follow-up decisions in the context of current melanoma management strategies.”

The full published study results can be accessed at the journal’s website.

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 3,100 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 five prospective risk of recurrence studies including more than 780 patients. Prediction of the likelihood of sentinel lymph node positivity has also been validated in two prospective multicenter study cohorts that included more than 1,400 patients. 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.

More information about the test and disease can be found at www.SkinMelanoma.com.

About Castle Biosciences

Castle Biosciences is a skin cancer diagnostics company dedicated to helping patients and their physicians make more informed decisions about treatment and follow-up care based on the individual molecular signature of the patient’s tumor. The Company currently offers tests for patients with cutaneous melanoma (DecisionDx^®-Melanoma, DecisionDx^®-CMSeq; www.SkinMelanoma.com) and uveal melanoma (DecisionDx^®-UM, DecisionDx^®-PRAME and DecisionDx^®-UMSeq; www.MyUvealMelanoma.com), with products in development for other underserved cancers, the most advanced of which is focused on patients with cutaneous squamous cell carcinoma. Castle Biosciences is based in Friendswood, Texas (Houston), and has laboratory operations in Phoenix, Arizona. More information can be found at www.CastleBiosciences.com.

DecisionDx-Melanoma, DecisionDx-CMSeq, DecisionDx-UM, DecisionDx-PRAME and DecisionDx-UMSeq are the trademarks of Castle Biosciences, Inc. Any other trademarks are the property of their respective owners.

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