GEP test for melanoma proves accurate in validation study

Recently released results of a clinical validation study suggest that a new gene expression profile (GEP) test is effective for cutaneous melanoma.

The study concludes that DecisionDx-Melanoma, a GEP test from Castle Biosciences Inc., Friendswood, Texas, accurately predicts metastatic risk in Stage I or Stage II melanoma patients who have no sign of disease beyond the original tumor. The study finds that the test can predict independent of current diagnostic modalities, including American Joint Committee on Cancer (AJCC) staging.

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In the multicenter study, formalin-fixed, paraffin-embedded specimens from biopsy or wide excision procedures of primary cutaneous melanoma tumors were analyzed to observe changes in the expression of 28 discriminating genes plus three 3 control genes. Based on the GEP test results, melanoma tumors were classified as either Class 1 or Class 2. Patients’ clinical outcomes at five years post-diagnosis were compared with the GEP test prediction.

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Kaplan-Meier analysis indicated that the five-year disease free survival (DFS) rates in the independent validation study were 97 percent and 31 percent for predicted Class 1 and 2 cases, respectively. These results compare favorably to results from a separate analysis of the development cohort, which found DFS rates of 100 percent and 38 percent.

Other findings:

·      The DecisionDx-Melanoma test accurately identified 120 of 134 Stage I and IIA cases without documented evidence of metastasis as Class 1

·      It correctly identified 24 of 30 Stage I and IIA cases with documented metastasis as Class 2

·      Of nine Stage I cases with documented metastasis, the test accurately classified five as Class 2

·      Conversely, the test accurately classified 104 of 110 Stage I cases without documented metastasis as Class I

Study author Pedram Gerami, M.D., director of melanoma research at Northwestern University’s Skin Cancer Institute, notes that past studies have shown that there are nearly twice as many melanoma-related deaths among stage I and II patients as there are among stage III and IV patients.

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“Hence, a significant and overwhelming majority of melanoma-related deaths come from patients classified as having lower-risk,” he tells Dermatology Times. “The GEP test for melanoma accurately identifies those stage I and II patients with biologically aggressive melanoma tumors who may potentially benefit from more rigorous monitoring and therapy. Additionally the GEP test result was an independent prognostic marker in multivariate analysis and was more accurate in separating low- and high-risk patient groups among our study patients compared to AJCC staging or other conventional staging parameters.”

Dr. Gerami adds that since many stage I and II patients are primarily followed by their dermatologists, the test can dermatologists determine which of these patients may benefit from more rigorous imaging, follow-up and possible adjuvant therapy.

“Also for those patients that are class I, [the test] can help relieve anxiety and potentially spare them unnecessary treatments or excessive imaging and follow-up,” he says.

References

The study appears in Clinical Cancer Research, a publication of the American Association for Cancer Research.

Gerami P, Cook RW, Wilkinson J, et al. Development of a prognostic genetic signature to predict the metastatic risk associated with cutaneous melanoma. Clin Cancer Res. 2015;21(1):175-83.