A blood test that monitors blood levels of DNA fragments from dead cancer cells may be better at tracking progression of metastatic melanoma than the current standard blood test.

The standard test measures blood levels of the enzyme lactate dehydrogenase (LDH), which tend to spike during aggressive tumor growth. LDH may also rise as part of other diseases and biological functions.  The new test looks at levels of circulating tumor DNA (ctDNA) that are released into the blood when tumor cells die and break apart to spill their contents.

Does it work?

In the new report, which appears in the January edition of <a href="http://www.moloncol.org/article/S1574-7891(15)00164-7/pdf"_blank">Molecular Oncology</a>, ctDNA levels in blood were elevated in 12 of 15 patients (80 percent) who were about to undergo treatment for metastatic melanoma. By contrast, blood levels of LDH were elevated before therapy in seven of 23 patients (30 percent). ctDNA could detect cancer recurrence, as confirmed by X-ray or CT scan, in 22 of 26 patients tested (85 percent) and undergoing therapy, while LDH was elevated in only 14 patients (54 percent), the study showed.

The ctDNA test was also helpful in patients with small tumors whose melanoma had spread. Specifically, ctDNA blood levels were elevated in five of seven such cases (71 percent), while LDH levels were elevated in only one of 13 (8 percent).

All study participants had one of the two most common genetic mutations linked to melanoma, BRAF or NRAS. All had ctDNA and LDH blood tests performed after therapy, and most before treatment. Normal blood levels of ctDNA were statistically determined by averaging results from 30 people who did not have melanoma.

“Our study results show that circulating tumor DNA is a superior blood test for evaluating and tracking progression of metastatic melanoma,” says senior study investigator David Polsky, MD, PhD, the Alfred W. Kopf, MD, Professor of Dermatologic Oncology at NYU Langone and director of its pigmented lesion section in the Ronald O. Perelman Department of Dermatology, in a news release.

Recent studies have suggested that ctDNA blood testing may be useful in monitoring progression of breast and colon cancers as well.

The number of immunological and targeted therapies for metastatic melanoma approved recently highlight the urgent need for a simple but more accurate blood test to monitor the disease.  Such a test would help to determine as early as possible when switching to an alternative therapy is warranted -- without the risk of infection and pain that accompany invasive needle biopsy and the radiation exposure that comes with X-ray or CT scans.

“A reliable blood test for tracking potential disease progression is preferred because blood tests offer feedback on what is happening throughout the body, while scans may not always visualize all parts of the body,” says Polsky,

Michelle Henry, MD, a dermatologic surgeon in New York City, is excited about the new findings. “A minimally invasive and specific blood test for advanced melanoma is huge,” she says.  “If this test proves to be as accurate as it seems in this paper, it’s a  a total game change.”

The new test could potentially allow melanoma patients to get the drugs they need sooner than they do today. The new crop of melanoma drugs come with a very high price tag.  “It will be helpful to say to insurers that the melanoma is is spreading and it’s spreading quickly,” she says.

“The ability to use peripheral blood to signal the return of a cancer could be very helpful to monitor patients,” adds Delphine J. Lee, MD, Director of the Carolyn Dirks and BrettDougherty Laboratory for Cancer Research and Department of Translational Immunology at John Wayne Cancer Institute at Providence Saint John's HealthCenter in Santa Monica, Calif. “ We need studies of a larger number of patients to validate whether the presence of cancer DNA detected in the blood will lead to better patient outcomes, particularly improved quality of life and overall survival.”