Metastatic melanoma disease activity may be monitored via circulating tumor DNA (ctDNA), which has higher sensitivity than lactate dehydrogenase (LDH) for detecting disease progression. These findings were reported in Molecular Oncology (doi:10.1016/j.molonc.2015.09.005).

Measures of the blood levels of the enzyme lactate dehydrogenase have been the standard test to inform treatment decisions for decades. Levels of the enzyme tend to spike during aggressive tumor growth, but are also known to rise as part of other diseases and biological functions. This alternative test looks at levels of ctDNA released into the blood when tumor cells die and break apart, spilling their contents into the bloodstream.

The research team from New York University Langone Medical Center, in New York City, found ctDNA levels were elevated in 12 of 15 patients (80%) who were about to undergo treatment for their metastatic melanoma. However, blood levels of LDH were elevated before therapy in only 7 of 23 patients (30%).

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The researchers used droplet digital PCR assays to detect BRAF and NRAS mutations. Overall, ctDNA was more sensitive than LDH in detecting melanoma metastasis.

Results also showed that ctDNA could detect cancer recurrence, as confirmed on radiograph or CT scan, in 22 of 26 patients tested (85%) and undergoing therapy, whereas only 14 patients (54%) were found to have elevated LDH levels.

In addition, ctDNA was found to be a sensitive indicator of disease progression, including metastases to the brain. In 10 of 12 cases of brain metastases (83%), ctDNA levels were elevated.

“Our study results show that circulating tumor DNA is a superior blood test for evaluating and tracking progression of metastatic melanoma,” said senior study investigator and dermatologist David Polsky, MD, PhD.

Polsky said recent studies suggest that testing for ctDNA levels in the blood may be useful in monitoring progression of breast and colon cancers as well. An accurate blood test is preferred by doctors and many patients because it avoids risks of infection and pain with invasive needle biopsy and radiation exposure with radiography or CT scans.