Researchers at the NYU Grossman School of Medicine and Perlmutter Cancer Center in the US have led an investigation of a test that monitors blood levels of DNA fragments released by dying tumour cells and can potentially act as an accurate early indicator of treatment success in individuals with late-stage metastatic melanoma.

Melanoma is one of the most aggressive forms of skin cancer.

The study analysed adults with undetectable levels of freely circulating tumour DNA (ctDNA) four weeks after drug treatment for metastatic melanoma tumours that are unresectable (cannot be removed surgically).

It showed that these patients, all with common genetic changes (BRAFV600 mutations) associated with cancer, were living nearly twice as long without cancer growth as those with detectable levels.

The investigators noted that physicians usually would have to wait three months before an X-ray, CT scan, or other measures to understand whether a tumour is growing or shrinking in response to treatment.

NYU Langone Health and Perlmutter Cancer Center Dermatologic Oncology professor David Polsky said: “Our findings suggest that levels of ctDNA may serve as a fast and reliable tool to gauge whether an anticancer medication is working.

“The blood test results could help support continuing the current treatment strategy or else encourage patients and physicians to consider other options.”

The study analysed blood samples from two pivotal clinical trials, involving 383 American, European, and Australian men and women. They were receiving targeted treatment with drugs dabrafenib and trametinib for unresectable metastatic melanoma tumours that had mutations in the BRAF gene.

Furthermore, the study found that patients with 64 or fewer copies of ctDNA per millilitre of blood before treatment were likely to respond well to therapy, surviving nearly three years on average.

The blood test is highly reliable as it could detect ctDNA in 93% of patients, the researchers noted.