Gene Expression Test Accurately Predicts Low SLN Positivity Risk in Melanoma
The DecisionDx-Melanoma test accurately identifies low sentinel lymph node risk in melanoma, according to the DECIDE study.
Artistic depiction of a melanoma cell targeted by shields, illustrating the cellular fight against skin cancer, emphasizing research and cure: © Татьяна Креминская - stock.adobe.com
The DecisionDx-Melanoma gene expression profile (GEP) test accurately determined which patients with melanoma were at low risk for sentinel lymph node (SLN) positivity, according to newly published data from the prospective, multicenter DecisionDx-Melanoma Impact on Sentinel Lymph Node Biopsy Decisions and Clinical Outcomes (DECIDE) study.1
Among 130 patients who were identified as low risk for SLN positivity using the DecisionDx-Melanoma test, none experienced melanoma recurrence at the time of last follow-up, translating to a 100% 3-year recurrence-free survival (RFS) rate. These findings suggest that the GEP test can safely guide decisions to forego SLN biopsy (SLNB) in select patients with T1 and T2 tumors.1,2
In this cohort, a “low-risk” result was defined as having less than a 5% predicted likelihood of SLN positivity. Of these patients, 48.5% underwent SLN biopsy, yielding a positivity rate of only 3.2%, while 51.5% were managed without SLN biopsy. No recurrences were observed regardless of whether the biopsy was performed.
“The current study demonstrates that patients with a class 1A result may safely forgo the SLNB procedure. No patients had a recurrence within the study period, regardless of SLN status, supporting the clinical value of the 31-GEP test in guiding patient care,” wrote study authors in findings published in Cancer Medicine.2
These results build on previously published data from the DECIDE study, which showed that the DecisionDx-Melanoma test results influenced 85% of SLNB decisions.1
Findings published in the World Journal of Surgical Oncology also showed that substantial proportions of T1 and T2 patients could potentially have avoided SLN biopsy without compromising diagnostic accuracy: 32.4% of T1a, 28.4% of T1b, 12.9% of T2a, and 12.5% of T2b cases.3
“These and other data suggest that the 31-GEP provides valuable prognostic information in multiple steps of the patient's clinical course,” added the study authors.2
Mechanism and Validation of the DecisionDx-Melanoma Test
DecisionDx-Melanoma is a GEP test that integrates tumor biology with clinical and pathological factors to stratify patients by risk of both SLN positivity and disease recurrence or metastasis. The test analyzes the expression of 31 genes within the primary tumor to determine a risk score. This is interpreted using a proprietary, validated algorithm.1
The result categorizes patients into risk classes, with class 1A indicating the lowest risk of SLN positivity and recurrence. The test's output is designed to be clinically actionable, supporting risk-aligned patient care. Further, the test is particularly relevant in patients with thin melanomas, specifically those with ≤2 mm Breslow thickness, where SLN biopsy decision-making can be highly individualized.
To date, DecisionDx-Melanoma has been evaluated in over 10,000 patient samples and supported by more than 50 peer-reviewed publications. Since its clinical launch, it has been ordered approximately 191,800 times (as of December 31, 2024).
DECIDE Study Design
The multicenter DECIDE study prospectively enrolled patients with T1 and T2 cutaneous melanoma who were being considered for SLN biopsy.1 Experts reviewed clinical and pathological factors alongside DecisionDx-Melanoma results to guide biopsy decisions. Post-treatment data included whether SLN biopsy was performed and the rationale behind that decision.2
Of those classified as low risk, the median age of patients was 65 years (range, 25-87), and median Breslow thickness was 0.9 mm (range, 0.2-1.9).The majority of patients had unknown ulceration status (96.9%). SLN status was known in 46.9% of cases, with the remaining unknown due to biopsy omission. Among these low-risk patients, tumor staging included 43.1% with T1b tumors, 33.1% with T1a, and 22.3% with T2a.
References
Publication of data from prospective, multicenter study demonstrates positive survival outcomes in patients with low-risk melanoma who avoided sentinel lymph node biopsy with information from Castle Biosciences’ DecisionDx®-Melanoma Test. News release. Castle Biosciences. April 3, 2025. Accessed April 7, 2025. https://tinyurl.com/bdd9rsz5
Guenther JM, Ward A, Martin BJ, et al. A prospective, multicenter analysis of recurrence-free survival after sentinel lymph node biopsy decisions influenced by the 31-GEP. Cancer Med. Published online April 1, 2025. doi:10.1002/cam4.70839
Guenther JM, Ward A, Martin BJ, et al. A prospective, multicenter analysis of the integrated 31-gene expression profile test for sentinel lymph node biopsy (i31-GEP for SLNB) test demonstrates reduced number of unnecessary SLNBs in patients with cutaneous melanoma. World J Surg Onc. 2025;23(1):5. doi:10.1186/s12957-024-03640-x
