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Gene profiling test identifies melanoma tumors likely to metastasize

Denver — In the battle against melanoma, a new test has shown that it can identify primary cutaneous melanomas that are likely to metastasize in patients who had negative sentinel lymph node biopsies (SLNB). Available since mid-2013, the product (DecisionDx-Melanoma, Castle Biosciences) uses gene expression profiling (GEP).

"SLNB is currently considered the strongest single prognostic parameter for melanoma," according to study author Pedram Gerami, M.D., who presented the data at the 72nd Annual Meeting of the American Academy of Dermatology. He is associate professor of dermatology and director of melanoma research at the Northwestern Skin Cancer Institute, Northwestern University, Chicago.

In a recent head-to-head test, "GEP testing performed superiorly to SLNB in our data set," he says.

The data include 217 patients to date who underwent both SLNB and GEP testing of their primary melanoma. Using sample tissue from the original biopsy, "We looked at several variables in determining how well these markers worked as prognosticating parameters," Dr. Gerami says. "One of them is positive predictive value — how accurately a positive test predicts a bad outcome." In this regard, he says, both tests performed roughly equally. In terms of negative predictive value, however, which gauges the accuracy of negative results, he says, GEP testing performed significantly better than SLNB: 79 versus 59 percent, respectively.

"This gives clinicians a better way of identifying high-risk patients. Currently, SLNB is our primary prognostic marker for patients who have intermediate or thick melanomas," he says. "And we know that of all the patients who end up having metastases, two out of three will have had a negative SLNB result. With SLNB, we are still missing a significant proportion of patients who will have aggressive disease."

Next: A way to identify high-risk patients despite negative SLNB


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