Blood test detects more than 50 types of cancer

A blood test that screens for more than 50 types of cancer could help doctors treat patients at an earlier stage than previously possible,a new study shows. The method was used to screen for more than 50 types of cancer — including particularly deadly variants such as pancreatic, ovarian, bowel and brain.

Researchers say the method — which can spot cancerous mutations before symptoms even appear — could spot particularly dangerous tumors that would otherwise go unnoticed.

The test looks for tell-tale changes to the DNA of dead cancer cells that leak into the blood as diseased tissues break down. 

In their findings, reported in the Annals of Oncology, experts said the procedure was best suited to detecting cancers at a later stage of development. However, the authors said further work could result in testing that would diagnose cancers at a far earlier stage than they would be otherwise.

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The test, developed by the Dana-Faber Cancer Institute and the Mayo Clinic, looks for molecules known as methyl groups that cause mutations in otherwise healthy cells, making them cancerous. It marks a change from more traditional methods that involve the sequencing of DNA.

"Our previous work indicated that methylation-based tests outperform traditional DNA-sequencing approaches to detecting multiple forms of cancer in blood samples," said Dana-Farber's Geoffrey Oxnard, a co-author of the study.

"The results of this study suggest that such assays could be a feasible way of screening people for a wide variety of cancers."
The research involved taking samples from almost 7,000 participants. In 96% of the tests, the samples correctly identified the tissue that the cancer had come from.

"Our results show that this approach to testing cell-free DNA in blood can detect a broad range of cancer types at virtually any stage of the disease, with specificity and sensitivity approaching the level needed for population-level screening," Oxnard said. "The test can be an important part of clinical trials for early cancer detection."

However, the experts said further work was needed. At present, they said, the possibility of tests not picking up cancers at their earlier stages — providing false reassurance — was too high.

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