New Blood Test Can Quickly Determine How Well Aggressive Skin Cancer Treatment is Working

The method currently being used to measure treatment success in people with later-stage skin cancer is CT scans every 3 months. The idea with the new blood test is that tests can be done more frequently and efficiently and results could be available within days. If doctors find that a specific method of treatment is not working, they would ideally be able to create a treatment plan more aligned with a person’s individual needs.

How is the blood test done?

The idea is to track the amount of tumor DNA in the blood. Cancer cells die and are replaced by new cells in a continual turnover as part of aggressive cancer growth. Because tumor cells burst as they die and spill DNA into the blood stream, researchers were able to measure this DNA and make treatment recommendations based on it.

For the study, researchers traced circulating tumor DNA (ctDNA) from the cancer gene BRAF. The BRAF gene plays a key role in tumor growth in an extremely deadly form of skin cancer called melanoma. For the study researchers will present at ASCO, blood from 224 people with stage 3 or 4 melanoma who carried BRAF mutations was analyzed. All of the patients in the study could not be treated surgically and were part of a clinical trial, which was testing drugs dabrafenib, trametinib, or a combination of the two. These two drugs were created to targeted BRAF-associated cancers.

What did the study find?

The key finding is that the tumor’s BRAF mutation was detected by the new test in 93 percent of people who carried it prior to beginning treatment. That ctDNA was no longer detectable after one month of therapy among the 80 patients who successfully responded to the treatment regiments in the trial.

“The significance of this study is that we found that measuring the mutated DNA before treatment started, and after 4 weeks of treatment, distinguished patients with longer or shorter survivals,” said Dr. David Polsky, a dermatologist at NYU Langone Health. “If a patient's mutated DNA was detectable prior to treatment, as it was in 93 percent of patients, and then became undetectable after 4 weeks on treatment, they had a longer survival than those who still had detectable DNA after 4 weeks of treatment.  We think the fact that we could still detect their DNA after 4 weeks of treatment meant that the drug treatment was less effective, which was in agreement with their generally shorter survival compared to the other group.”

Why is this finding important?

It is the largest study of the ctDNA blood test in metastatic melanoma, according to Dr. Polsky. “The study provides solid evidence to support more studies to evaluate additional on-treatment blood measurements to best determine how we may be able to use these tests moving forward.”

Even though the blood test requires additional studies and clinical trials, researchers are hopeful that monthly monitoring of circulating tumor DNA in patients being treated for late-stage melanoma can provide early indication of if/how well treatment is working — resulting in more successful treatment plans, and more people surviving this disease.

Learn more about SurvivorNet's rigorous medical review process.