A simple blood test detects cancer years earlier than previously possible

Scientists from the Memorial Sloan Kettering Cancer Centre and Grail, a genomics company dedicated to early cancer detection and backed by Jeff Bezos and Bill Gates, announced at this week’s 2017 American Society of Clinical Oncology (ASCO), that they’ve successfully trialled a new type of non-invasive cancer test that paves the way for a future when we'll be able to get highly accurate cancer screening with just a simple blood test.

The technology, a “Liquid biopsy,” works by scanning the patients blood for small fragments of DNA shed by tumors in the body, and increasingly it’s looking like it could usher in a new era in cancer diagnostics because right now the best method we have of testing for cancer is to perform a biopsy, where a small piece of the tissue is cut out and sent away for lab analysis. But biopsies are painful and invasive and you already have to have cancer, or at least be suspected of having it, before you can be tested.

The new method works by finding what is called circulating tumour DNA (ctDNA) in a person’s blood stream, something that until now has been hard to analyse accurately.

"Our findings show that high intensity circulating tumour DNA sequencing is possible and may provide invaluable information for clinical decision-making, potentially without any need for tumour tissue samples," said lead researcher Pedram Razavi.

During the trial the team used blood and tissue samples from 124 metastatic breast cancer, lung cancer, and advanced prostate cancer patients and scanned the samples for 508 different gene mutations. The test then analysed each genome over 60,000 times to produce at least hundred times more data than other sequencing methodologies, and it was this that helped make the trial a success.

To see whether the method could catch any tumour DNA floating around in the blood, the team then compared the results with those from tissue samples and genetic material from the patients' own white blood cells.

"Our combined analysis of cell-free DNA and white blood cell DNA allows for identification of tumour DNA with much higher sensitivity, and deep sequencing also helps us find those rare tumour DNA fragments," said Razavi.

The researchers detected 864 genetic changes across all three types of cancers in the tissue samples, and found 73 percent of those in the blood tests as well.

In 89 percent of the patients, they found at least one mutation in both tumour tissue and in blood, and for breast cancer, for example, the success rate was 97 percent. But perhaps one of the biggest benefits of having highly sensitive ctDNA tests is the chance of finding cancers years earlier than is possible with today’s biopsies, catching them before they have time to spread through the body - and if you can catch it sooner you can treat it sooner which means that more people live to tell the tale of their close encounter with cancer.

"It's an important first step. We show that what we call a high-intensity approach works," said Razavi .