Late-Breaking EADV 2026 Data Support Use of DecisionDx®-Melanoma in SLNB Decision-Making and Risk-Aligned Post Surgical Management

Data show patients with low-risk DecisionDx-Melanoma i31-SLNB results had sentinel lymph node (SLN) positivity below 5% when biopsied, and eligible patients who avoided SLNB had five-year recurrence-free survival (RFS) of 99.6%

Separate ePoster shows DecisionDx-Melanoma identifies early-stage, transected melanomas with recurrence risk similar to that seen in stage IIB disease, supporting closer surveillance when staging is uncertain

FRIENDSWOOD, Texas, Sept. 30, 2026 /PRNewswire/ -- Castle Biosciences, Inc. (Nasdaq: CSTL), a company improving health through innovative tests that guide patient care, will present new data on DecisionDx-Melanoma at the European Academy of Dermatology and Venereology (EADV) Congress 2026, taking place Sept. 30–Oct. 3 in Vienna, Austria.

A late-breaking oral presentation will highlight the largest prospective, multi-center study of gene expression profiling (GEP) in cutaneous melanoma to date, involving 2,799 patients across 29 U.S. centers. The findings support using DecisionDx-Melanoma to identify patients who may safely forgo SLNB and patients with early-stage disease whose higher recurrence risk may warrant closer surveillance.

"Staging is an essential starting point, but understanding a patient's tumor biology can help us make more informed recommendations about sentinel lymph node biopsy and follow-up care," said Joseph Gadzia, M.D., study author and board-certified dermatologist and Mohs micrographic surgeon at Kansas Medical Center in Topeka, Kansas. "Seeing excellent outcomes among patients with low-risk i31-SLNB results who did not undergo SLNB in this large, prospective study should give physicians greater confidence in using DecisionDx-Melanoma results to help guide these important decisions with their patients."

Late-Breaking Oral Presentation

• Abstract LB-339: The integrated 31-gene expression profile (i31-SLNB) identifies patients with a low risk of sentinel lymph node positivity and 31-GEP identifies patients with high 5-year recurrence risk: The largest prospective, multicenter study of GEP for cutaneous melanoma
• Session: D2T01.3 - Late Breaking News
• Room: Hall A
• Date and Time: Thursday, Oct. 1; 14:45 - 15:00 CEST
• Key findings: This multi-center, prospective study enrolled 2,799 patients across 29 U.S. centers to evaluate DecisionDx-Melanoma's ability to predict sentinel lymph node (SLN) positivity and stratify recurrence risk.
  • Among 676 patients who underwent SLNB and received an i31-SLNB result, those classified as low risk (<5% predicted risk) had an observed SLN positivity of 4.4%, consistent with the test's predicted risk of less than 5%. By comparison, patients classified as high risk (>10% predicted risk) had an observed SLN positivity rate of 22.8%.
  • Among 565 SLNB-eligible patients with low-risk i31-SLNB results who did not undergo the SLNB procedure, five-year RFS was 99.6%.

Together, these findings support using the test's i31-SLNB result to identify low-risk patients who may safely forgo SLNB and patients whose higher-risk result supports consideration of the procedure.

DecisionDx-Melanoma's 31-GEP Class result also significantly stratified five-year recurrence risk and provided prognostic information beyond traditional staging. Patients with early-stage disease (stage I–IIA) and high-risk Class 2B results had RFS similar to patients with stage IIB disease, supporting consideration of closer surveillance and additional treatment for patients whose higher risk may not be fully captured by staging alone.

A second abstract on DecisionDx-Melanoma will also be shared at EADV via an ePoster.

• Title: The 31-gene expression profile test for cutaneous melanoma accurately identifies patients with transected tumors at high and low 5-year risk of recurrence
• Key findings: When a biopsy cuts through the base of a melanoma, known as transection, the sample may not capture the tumor's full thickness. Because thickness helps determine melanoma stage, this can leave uncertainty about a patient's risk and how closely they should be monitored.
  
  In a multi-center analysis of 687 patients with transected melanomas, DecisionDx-Melanoma significantly stratified patients at high and low risk of recurrence. Five-year RFS was 93.2% for patients with low-risk (Class 1A) results versus 64.1% for those with high-risk (Class 2B) results (p<0.001). Among patients with early-stage disease (stage I–IIA), those with Class 2B results had five-year RFS of 73.7%, similar to those with stage IIB melanoma and worse than those with stage IIIA.
  
  These findings support using DecisionDx-Melanoma to help tailor care when initial staging is uncertain. Low-risk (Class 1A) results, which were most common in the study, may support less intensive follow-up. High-risk (Class 2B) results in patients with early-stage disease may warrant closer surveillance and consideration of imaging that would not typically be recommended based on their stage alone.

Castle will also present an encore of previously reported validation data for its AdvanceAD-Tx™ test via an ePoster titled, "The 487-gene expression profile test guides systemic therapy selection to improve outcomes for patients with atopic dermatitis: Results from a prospective, multi-center trial." These data have now been published in the Journal of the American Academy of Dermatology.

About DecisionDx-Melanoma
DecisionDx-Melanoma is a gene expression profile (GEP) test designed to analyze tumor biology to deliver a personalized risk assessment for patients with stage I–III cutaneous melanoma, enhancing risk stratification beyond American Joint Committee on Cancer (AJCC) staging alone. By combining molecular insights with select clinicopathologic features, the test provides two distinct outputs: a personalized risk of sentinel lymph node (SLN) positivity and a personalized risk of recurrence and/or metastasis. This clinically actionable information is designed to help guide risk-aligned patient management decisions, including SLN biopsy consideration, follow-up intensity, imaging and referrals.

DecisionDx-Melanoma is supported by 58 peer-reviewed publications, including prospective studies and meta-analyses, and was developed in collaboration with more than 100 leading U.S. institutions. The test has been clinically validated in more than 10,000 patient samples, ordered more than 240,000 times since launch, and has been shown to be associated with improved patient survival. Learn more at www.CastleBiosciences.com.

About AdvanceAD-Tx
AdvanceAD-Tx is a non-invasive gene expression profile (GEP) test designed to guide systemic treatment decisions for patients aged 12 years and older with moderate-to-severe atopic dermatitis (AD). Using RNA expression data from lesional skin scraping samples—no biopsy required—the test evaluates 487 genes across 12 inflammatory and cutaneous biology pathways to reveal the underlying immune biology driving an individual patient's disease. The test classifies patients into one of two molecular profiles: a Janus kinase (JAK) Inhibitor Responder Profile or a T helper type 2 (Th2) Molecular Profile.

The prospective clinical validation study showed that patients with a JAK Inhibitor Responder Profile given JAK inhibitor therapy experienced significantly greater clinical benefit — including improved and faster skin clearance (EASI-90), greater likelihood of achieving no itch and remaining flare-free, and better quality of life by three months —  compared to those treated with a Th2-targeted therapy. AdvanceAD-Tx provides clinicians with objective, molecular-based insights to help personalize systemic treatment decisions and improve care for patients. Learn more at https://castlebiosciences.com/tests/therapy-guidance/advancead-tx/overview.

About Castle Biosciences
Castle Biosciences (Nasdaq: CSTL) is a leading diagnostics company improving health through innovative tests that guide patient care. With a primary focus in dermatologic and gastroenterological disease, we develop personalized, clinically actionable solutions that help improve disease management and patient outcomes.

We put people first—empowering patients and clinicians and informing care decisions through rigorous science and advanced molecular tests that support more confident treatment planning. To learn more, visit www.CastleBiosciences.com and connect with us on LinkedIn, Instagram, Facebook and X. 

DecisionDx-Melanoma, DecisionDx-CMSeq, i31-SLNB, i31-ROR, DecisionDx-SCC, MyPath Melanoma, AdvanceAD-Tx, TissueCypher, Esopredict, 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: DecisionDx-Melanoma's ability to (i) identify patients who may safely forgo SLNB or patients whose higher-risk result supports consideration of the procedure based on their i31-SLNB result, (ii) stratify recurrence risk and provide prognostic information beyond traditional staging, (iii) support consideration of closer surveillance and additional treatment for patients with early-stage disease whose higher risk may not be fully captured by staging alone, and (iv) help tailor care for patients with transected tumors when initial staging is uncertain; and AdvanceAD-Tx's ability to guide systemic therapy selection to improve outcomes for patients with atopic dermatitis. The words "believe," "can," "may," "support," "designed to," "help," "will," "should" 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 these studies, including with respect to the discussion of our tests 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 Annual Report on Form 10-K for the year ended December 31, 2025, and our subsequent Quarterly Reports on Form 10-Q, each as filed or to be filed with the SEC, 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.

Investor Contact:
Camilla Zuckero
[email protected] 

Media Contact:
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SOURCE Castle Biosciences, Inc.