New blood test can detect 50 types of cancer
New blood test can detect 50 types of cancer
System uses machine learning to
offer new way to screen for hard-to-detect cancers
The test is based on DNA that is shed by tumours and found
circulating in the blood. More specifically, it focuses on chemical changes to
this DNA, known as methylation patterns.
Researchers say the test can not
only tell whether someone has cancer, but can also shed light on the type of
cancer they have.
Dr Geoffrey Oxnard of Boston’s
Dana-Farber Cancer Institute, part of Harvard Medical School, said the test was
now being explored in clinical trials. “You need to use a test like this in an
independent group at risk of cancer to actually show that you can find the
cancers, and figure out what to do about it when you find them,” he said.
Writing
in the journal Annals of Oncology, the team reveal how the test was developed
using a machine learning algorithm – a type of artificial intelligence. Such
systems pick up on patterns within data and as a result learn to classify it.
The team initially fed the system
with data on methylation patterns in DNA from within blood samples taken from
more than 2,800 patients, before further training it with data from 3,052
participants, 1,531 of whom had cancer and 1,521 of whom did not.
Using this information, the
system sorted the samples into groups based on the methylation patterns. The
team then taught the system which groups reflected which type of cancer.
“In pregnant women we look in
their free-floating DNA for foetal abnormalities,” said Oxnard. “We know this
[approach] exists, the question is how do you fine-tune and perfect the art of
looking for cancer in this free-floating DNA? And that is what the machine
learning did.”
The team then tested the trained
system on another set of samples from 1,264 individuals, about half of whom had
cancer.
The results reveal that less than
1% of those without cancer were wrongly identified by the system as having the
disease. “It is really important you don’t tell non-cancer patients they have
cancer,” said Oxnard.
When it came to identifying
people with cancers the team found that, across more than 50 different types of
cancer, the system correctly detected that the disease was present 44% of the
time – although the team stress that figure could differ if the test was used
to screen a general population, rather than those known to have cancer.
Detection was better the more
advanced the disease was. Overall, cancer was correctly detected in 18% of
those with stage I cancer, but in 93% of those with stage IV cancer.
The team say the results are
exciting as they offer the possibility of a new way to screen for cancers that
are otherwise difficult to detect. For example, the system correctly identified
63% of those with stage I pancreatic cancer, rising to 100% in stage IV.
The team further found that the
system could shed light on the type of cancer. For 96% of samples deemed to
show cancer, the test was able to offer a prediction for in which the tissue
the cancer originated, with 93% of these predictions found to be correct.
Dr David Crosby, head of early
detection at Cancer Research UK, said that detecting cancers in their early
stages is important as they are less aggressive and more treatable.
Although this test was still at
an early stage of development, the initial results were encouraging, he said.
“And if the test can be fine-tuned to be more efficient at catching cancers in
their earliest stages, it could become a tool for early detection.”
But Crosby added there was work
to do. “More research is needed to improve the test’s ability to catch early
cancers and we still need to explore how it might work in a real cancer
screening scenario,” he said.
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