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DENVER – A gene expression profile test was an independent predictor of metastasis of primary cutaneous melanomas in patients with negative sentinel lymph node biopsies.
The DecisionDx-Melanoma test is useful for identifying a high-risk group of patients with negative sentinel lymph node biopsy results, said Dr. Pedram Gerami of the department of dermatology and director of melanoma research at the Northwestern University, Chicago, Skin Cancer Institute. The test "is an independent predictor of metastasis and death, and significantly improves upon sentinel lymph node biopsy for staging melanoma patients."
The results of the DecisionDx-Melanoma test, a noninvasive 31-gene expression profile (GEP) test, were compared with the results of sentinel lymph node biopsy (SLNB) in 134 patients who had stage I, II, or III cutaneous melanoma and underwent a documented sentinel lymph node procedure. Of the 134 patients, 28 had positive sentinel lymph nodes and 91 had positive (class 2, high risk) GEP results.
Dr. Pedram Gerami
Metastases developed over a subsequent 5-year period in 18 of the 28 patients with positive SLNB and in 62 of the 91 patients with positive GEP results. Metastases developed in 51 of the 106 patients with negative SLNB and in 7 of 43 patients with negative (class 1, low risk) GEP results.
While the positive predictive value of the two tests were comparable, the ability of GEP to predict negative outcomes was significantly better than that of SLNB (P less than .0001), Dr. Gerami reported at the annual meeting of the American Academy of Dermatology.
The rate of 5-year metastasis-free survival (MFS) was 55% for 106 patients with negative SLNB, compared to 37% for 28 patients with positive SLNB (P = .003). The GEP test results showed improved prognostic accuracy in these same patients with an MFS of 87% for the 43 patients with negative GEP (class 1, low risk) results and of 31% for the 91 patients with positive GEP (class 2, high risk) results (P less than .0001).
Differences in overall survival (OS) paralleled the MFS rates, with SLNB-negative patients having a 5-year OS of 67% and SLNB-positive patients having a 5-year OS of 55% (P = .024). OS for negative GEP (class 1, low risk) patients was 92% and for positive GEP (high risk, class 2) was 49% (P less than .0001).
Use of the GEP test also was analyzed in combination with SLNB status. As expected, the 20% of patients (n = 27) who had high-risk results for both tests (GEP class 2 and SLNB-positive findings) had lower survival rates (MFS, 34%; OS, 53%). Similarly, the 31% of patients (n = 42) who had low-risk results for both tests (GEP class 1 and SLNB-negative findings) had higher survival rates (MFS, 82%; OS, 92%).
Importantly, the MFS was 31% and the OS was 49% at 5 years in the 64 patients who had SLNB-negative results but class 2 GEP test results, Dr. Gerami said. Cox multivariate analysis comparing the GEP test to SLNB showed the GEP test to be the only independent and highly significant prognostic factor in this analysis (P less than .000003).
Dr. Gerami has been a consultant to Castle Biosciences. The DecisionDx-Melanoma test is a product of Castle Biosciences, the sponsor of the study. More information about the test can be found at www.skinmelanoma.com.
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