Melanoma Experts Say 'No' to Routine Gene Profile Testing

M. Alexander Otto, MMS, PA

August 26, 2020

An international panel of 49 melanoma specialists has come out against routine gene expression profile (GEP) testing for cutaneous melanoma, pending solid proof of clinical benefit.

"The currently published evidence is insufficient to establish that routine use of GEP testing provides additional clinical value for melanoma staging and prognostication beyond available clinicopathologic variables," they argue.

Patients must be protected "from potentially inaccurate testing that may provide a false sense of security or perceived increased risk," leading to the wrong decisions, they said in a consensus statement from the United States' national Melanoma Prevention Working Group.

The statement was published on July 29 in JAMA Dermatology.

The GEP test for melanoma that is available in the US — DecisionDx-Melanoma from Castle Biosciences — checks the expression levels of 31 genes reported to be associated with melanoma metastasis and recurrence. It uses quantitative reverse transcriptase and polymerase chain reaction on RNA from formalin-fixed, paraffin-embedded biopsy specimens.

The test stratifies patients as being at low, intermediate, or high risk.

It is marketed as a guide to whether to perform sentinel lymph node biopsies (SLNB) on patients age 55 years or older with tumors less than 2 mm deep, and to decide what levels of follow-up, imaging, and adjuvant treatment are appropriate for tumors at least 0.3 mm deep.

Medicare reimburses at $7,193 per test for SLNB-eligible patients.

However, this test is not endorsed by the American Academy of Dermatology or National Comprehensive Cancer Network outside of studies because the evidence of benefit is not strong enough, the consensus authors note.

Even so, use of the test is growing, with up to 10% of cutaneous melanomas now being tested in the United States.

Company Welcomes "Further Discussion"

"To date, thousands of clinicians — over 4200 US clinicians in the last 12 months — have utilized our GEP test for cutaneous melanoma in their patients after reviewing our clinical data and determining that our test provides clinically actionable information that complements current melanoma staging," said Castle Biosciences Vice President of Research and Development Bob Cook, PhD, when asked for comment.

Citing company-funded studies, he said that "the strength of the existing evidence in support of these claims has undergone rigorous evaluation to obtain Medicare reimbursement."

"We believe that the application of the test to help guide [the] decision to pursue SLNB has the potential to realize significant cost savings by reducing unnecessary SLNB procedures, particularly in the T1 population."

Asked for a reaction to the consensus statement, Cook told Medscape Medical News: "We recently launched two prospective studies with multiple centers nationwide that will involve thousands of patients and provide additional data relating our tests to patient outcomes.… We welcome further discussions to promote collaborative efforts with centers that are part of the [Melanoma Prevention Working Group] to improve patient outcomes."

Cart Before the Horse

Medicare, although it reimburses the test, has its doubts. Due to the "low strength of evidence," the Centers for Medicare & Medicaid Services said in their local coverage determination that continued reimbursement depends on demonstration of 95% or greater distant-metastasis-free survival and melanoma-specific survival at 3 years "in patients directed to no SLNB by the test compared to standard of care, and...evidence of higher SLNB positivity in patients selected for this procedure by the test compared to standard of care."

The statement hints at the Achilles' heel of GEP in melanoma — ie, the lack of evidence that test results improve outcomes. This was the main concern of the consensus statement; the cart is before the horse.

One of the consensus authors, David Polsky, MD, PhD, a professor of dermatologic oncology at New York University, Manhattan, said that "most of the data for this test come from retrospectively collected patient groups." The prospective studies have been generally small, with no comparator group. "While they have shown some promise in intermediate thickness melanoma, they have not yet demonstrated utility for thin, stage I melanomas."

First, Do No Harm

A new meta-analysis of over 800 patients with cutaneous melanoma tested by DecisionDx-Melanoma, published in JAMA Dermatology alongside the consensus statement, shows how the tests perform.

Among patients with a recurrence, DecisionDx-Melanoma correctly classified 82% with stage II disease but only 29% with stage I disease as high risk. Among those without recurrence, the test correctly classified 90% of stage I patients but only 44% with stage II disease as low risk.

Similar results were seen with the melanoma GEP test available in Europe, MelaGenix (NeraCare GmbH). This test was developed from a panel that was narrowed to seven protective genes and one high-risk gene using a training cohort of 125 cutaneous melanomas.

"The prognostic ability of GEP tests...appeared to be poor at correctly identifying recurrence in patients with stage I disease, suggesting limited potential for clinical utility in these patients," comment the meta-analysis authors, led by Michael Marchetti, MD, an assistant professor of dermatology at Weill Cornell Medical College in New York City.

"Unknown are the harms associated with a false-positive result, which were 10-fold more frequent than true-positive results in patients with stage I disease," they point out.

"Further research is needed to define the incremental improvement in risk predictions provided by the test beyond...all other known clinicopathologic factors," which include patient sex, age, tumor location and thickness, ulceration, mitotic rate, lymphovascular invasion, microsatellites, and other factors proven to be linked to outcomes, they said.

Studies so far suggesting benefit have incorporated a few of those factors, but not all of them. For now, "it is not clear which patients should be tested or how to act on the results," Marchetti and colleagues conclude.

Breast Cancer Standard of Proof

Larger, prospective studies are needed to address whether GEP testing can replace SLNB to predict relapse "and [can identify] patients who could be spared surveillance imaging and/or benefit from adjuvant therapy," say the consensus authors. Follow-up also needs to be long enough to detect delayed recurrence of thin melanomas, they add.

With more research, there is reason to hope that gene expression profiling will help in melanoma; it's already standard of care in breast cancer, they point out.

On the hope front, one cohort study evaluated whether DecisionDx-Melanoma could identify patients at low risk for positive lymph nodes in T1/T2 disease who were eligible for biopsy. Only 1.6% of subjects who were age 65 years or older and pegged by the test as low risk had a positive node.

"This is a promising direction of investigation...in a narrow, defined population," said authors led by Carrie Kovarik, MD, associate professor of dermatology at the University of Pennsylvania, Philadelphia, in an opinion piece last spring.

But still, until there's "clear evidence that [DecisionDx-Melanoma] results affect patient outcomes, we should not use it to influence care decisions in patients with thin" melanomas. Dermatology "should expect the same standards" of proof as breast cancer, they said.

What to do Right Now?

Despite the marketing, "think twice before ordering GEP tests for" T1a melanomas is the message in an editorial that accompanies the consensus statement. The 5- and 10-year melanoma-specific survival rates are 99% and 98%, respectively. "GEP tests will unlikely change these estimates significantly. In fact, the new meta-analysis indicates "that there may be an approximately 12% misassignment rate in this population," write editorialists Warren Chan, a medical student at Baylor College of Medicine, Houston, and Hensin Tsao, MD, PhD, director of the melanoma genetics program at Massachusetts General Hospital, Boston.

"Even if you use GEP testing and discover a low-risk class assignment for a 2 mm thick melanoma, avoid the urge to bypass the sentinel lymph node discussion…. Nodal sampling, for good reasons, remains part of all major guidelines and determines eligibility for adjuvant treatments.... Many of us engaged in genomics research believe that accurate [melanoma] GEP will be developed in time, but better tools and greater tenacity are needed," they wrote.

There was no industry funding for the consensus statement and meta-analysis. Authors on the consensus statement reported numerous ties to pharmaceutical and other companies, as listed in the paper.

M. Alexander Otto is a physician assistant and award-winning medical journalist who has worked previously for several major news outlets, including McClatchy and Bloomberg BNA. He is an MIT Knight Science Journalism fellow. Email: aotto@mdedge.com.

JAMA Dermatol. Published online July 29, 2020. Consensus Statement Abstract, Meta-analysis Abstract, Editorial; and 2020;156:837-838. Opinion Piece Abstract

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