A personalised blood test can tell whether treatments for breast cancer are working, and possibly save people from unnecessary surgery, according to early results. If the test can be validated, it could be used to identify who is at risk of relapse, say the researchers behind the work.
The test has been developed for people in the early stages of breast cancer. After receiving a diagnosis, people are typically prescribed drugs to shrink their tumours before surgeons attempt to remove them.
Sometimes, this drug treatment is enough. By the time they have their surgery, around 30 per cent of people will have undetectable levels of tumour DNA, says Muhammed Murtaza at Translational Genomics Research Institute in Phoenix, Arizona.
Advertisement
“You treat patients quite aggressively, but a lot of patients might get treatment they didn’t need,” he says. Another 10-15 per cent of people will relapse, suggesting they might have needed more treatment.
Ideally, a blood test given after drug treatment but before surgery would predict what types of treatment how much treatment any individual needs. Similar tests exist for cancers that have spread throughout the body, but it has been difficult to create one that is sensitive enough to pick up on the tiny amount of tumour DNA left in the blood of someone with early-stage cancer who has had their tumour shrunk.
Murtaza and his colleagues have developed a new, more sensitive test. In their approach, the team started by analysing biopsies taken from tumours of people with breast cancer. They used these to identify a set of around 30 mutations specific to each individual.
They then created personalised tests that can catch any one of the 30-odd mutations an individual’s tumour might have, instead of using single tests to search for each specific mutation. This technique, along with others that improve its efficiency, has enabled the team to develop a test that is 100 times more sensitive that existing ones, says Murtaza.
When the team tried their test on blood samples from 33 people with early-stage breast cancer, they were able to find mutations in all of them. Murtaza’s team also looked at blood from 22 of these individuals after they had been given treatment to shrink their tumours, and again after surgery.
There was a clear difference in the pre-surgery results of people who went on to have detectable tumours in their surgeries compared to those who appeared to be cancer-free during their operations. This suggests the test might reveal who needs surgery and who doesn’t.
Once the original tumour mutations are nailed down, future tests could be done in a couple of days, so the test could give close to a real-time indication of how well any treatment is working, says Murtaza. His team is working to validate the test in another study with 100 participants, and they hope the test will be available as part of clinical trials within the next two years.
“It will be really useful for clinicians and patients to get information [on how treatments are working] in real time rather than six months down the line when it might be too late,” says Jacqui Shaw at the University of Leicester. She points out that several other teams, including her own, are working on similarly sensitive tests.
“These techniques can potentially capture relapse before imaging can…we could catch [cancer relapse] at an early stage and potentially cure it,” says Lorenzo Gerratana at the University of Udine in Italy. “I personally think that these tests will change the way we treat patients,” he says.
Science Translational Medicine
