DecisionDx test can help identify sentinel lymph node risk

Key takeaways:

• Up to 88% of sentinel lymph node biopsies (SNLB) return with a negative result.
• The DecisionDx-Melanoma test, which uses gene expression profiles to stratify risk, was found to reduce SLNB need by 33%.

The melanoma 31-gene expression profile test can help physicians to better estimate risk for sentinel lymph nodes, possibly reducing the need for biopsies, according to a study.

“We are probably doing more sentinel lymph node biopsies (SLNB) than necessary,” Joseph J. Bennett, MD, MBA, FACS, FSSO, system chief of surgery at LifeBridge Health, chief of surgery at Sinai Hospital of Baltimore, chair of surgery at Northwest Hospital and one of the study’s authors, told Healio. “While I’m not suggesting surgeons go against the [National Comprehensive Cancer Network] guidelines, there are biological features of a melanoma that don’t get captured by traditional [American Joint Committee on Cancer] staging. This is where the gene expression profile testing becomes important as it further elucidates a melanoma’s aggressiveness.”

SLNB has been shown in previous studies to improve disease-free survival in patients with melanoma; however, up to 88% of SLNBs return with a negative sentinel lymph node (SLN) result.

In this study, SLNB was offered to all patients with a melanoma sized 0.8 mm or larger and patients with a melanoma of at least 0.6 mm and a shave biopsy with a positive margin. All 156 patients also had a 31-GEP test (DecisionSx-Melanoma, Castle Biosciences) and analysis. Using the integrated 31 (i31)-GEP, the researchers assigned cases at less than 5% or 5% and greater SLN positivity risk and were compared with T-stage using T1a.

An SLN positivity rate of 20.5% was found, with 17 patients having T1 tumors and 15 patients having at least one high-risk factor, defined as a mitotic rate of at least 2 per mm², presence of regression, lymphovascular invasion, microsatellites, transected base, absence of tumor-infiltrating lymphocytes or age younger than 40 years.

The i31-GEP found 19.2% of patients overall had a less than 5% risk for SLN positivity. T1 tumors were present in 29% of patients and T2 in 30%. Of these patients, i31-GEP identified 33% as having a less than 5% risk.

Additionally, the test reclassified patient risk as less than 5% in 51.2% of patients whose risk was 5% to 10% by current guidelines, and as less than 10% in 11.6%. In total 62.7% of cases were reclassified to a status that better defined if the SLNB procedure was necessary.

In 30 patients with a more than 10% predicted risk by the i31-GEP who also had T1-T2 tumors, the SLN positivity rate was 33.3%, compared with 31.9% of T3-T4 patients.

Of 91 patients with T1-T2 tumors, 30 of them were identified as low-risk by the i1-GEP test, showing a reduction of possible SLNB of 33%.

“By taking such genetic mutations into consideration, in addition to the important clinical staging as per TNM status, we can better risk stratify patients who are more or less likely to have nodal metastases and be more selective than we are currently doing,” Bennett told Healio. “The study showed that by using the GEP, we could avoid doing many unnecessary procedures while at the same time, not missing a cancer accidentally if it’s present.”

Reference:

• DecisionDx-Melanoma can identify melanoma patients with low risk of sentinel lymph node positivity who may safely forego biopsy surgery, new independent study affirms. https://ir.castlebiosciences.com/news/news-details/2024/DecisionDx-Melanoma-Can-Identify-Melanoma-Patients-with-Low-Risk-of-Sentinel-Lymph-Node-Positivity-Who-May-Safely-Forego-Biopsy-Surgery-New-Independent-Study-Affirms/default.aspx. Posted Sept. 11, 2024. Accessed Sept. 11, 2024.