Gene Test Predicts Melanoma Metastases

A gene expression profile (GEP) test can identify primary cutaneous melanoma tumors that are likely to metastasize in patients who had a negative sentinel lymph node biopsy.

The noninvasive 31-gene GEP test that is widely used to determine metastatic risk in Stage I and II melanoma patients has been compared to sentinel lymph node biopsy (SLNB) which has traditionally been the best prognostic test available for melanoma patients.

Scientists at Castle Biosciences Inc. (Friendswood, TX, USA) compared their test called DecisionDx-Melanoma to results from134 patients with Stage I, II, or III cutaneous melanoma. These 134 patients represented all patients in the initial clinical validation studies who had a documented sentinel lymph node procedure. The DecisionDx-Melanoma is a proprietary test carried out in the company’s laboratories.

In patients with a negative SLNB, a result interpreted as a lower risk for metastasis, the GEP test identified the vast majority of melanomas that ultimately progressed over the subsequent five year period. The rate of five year metastasis-free survival (MFS) was 55% for SLNB negative patients compared to 37% for SLNB positive patients The GEP test results showed improved prognostic accuracy in these same patients with an MFS of 87% for the low-risk (Class 1) patients and 31% for the high risk (Class 2) patients.

The GEP test showed improved prognostic accuracy, with an overall survival (OS) for GEP Class 1 patients of 92% compared to 49% for Class 2 patients. The GEP test was also analyzed in combination with SLNB status. The 20% of patients who had high risk results for both tests (GEP Class 2 and SLNB positive) had lower survival rates (MFS=34%; OS=53%). Similarly, the 31% of patients who had low risk results for both tests (GEP Class 1 and SLNB negative) had higher survival rates (MFS=82%; OS=92%). Importantly, in the 49% of patients who had results that were discordant, high risk outcome for one test, low risk for the other, the GEP test result correctly predicted the patients' clinical outcomes. Net reclassification improvement of GEP class over SLNB status was greater than 50%.

Pedram Gerami, MD, the study author and an associate professor of Dermatology at Northwestern University (Evanston, IL, USA), said, “The results from this study show the GEP test is an independent predictor of metastasis and death, and significantly improves upon sentinel lymph node biopsy for staging melanoma patients. Based upon this data, optimal use of the GEP test may be to identify high risk patients among those with a negative SLNB result, or for patients who are ineligible for or who decline a SLNB procedure.” The study was presented at the 72nd Annual Meeting of the American Academy of Dermatology held March 21-25 2104 in Denver, CO, USA).

Castle Biosciences Inc.
Northwestern University

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