New research suggests that blood tests known as “liquid biopsies” can improve the treatment of some people with metastatic breast cancer and help their tumors remain under control for more than a year.
For many, it’s been a long time coming: More than a decade ago, researchers and investors predicted that liquid biopsies — which are sensitive enough to detect tumor cells and DNA in the blood — would be “game changers” in the realm of cancer.
Although liquid biopsies haven’t replaced standard cancer screening methods like mammograms and colonoscopies, the new study and others like it demonstrate that the blood tests can help doctors monitor cancer and help them select treatments likelier to work.
Liquid biopsies are so sophisticated that they can detect minuscule bits of DNA that have leaked out of tumor cells and are floating freely in the blood. The most sensitive liquid biopsies, like those used in the new study, go one step further, detecting ominous changes in key proteins in cancer cells.
The research — published Sunday in The New England Journal of Medicine and presented at the American Society of Clinical Oncology’s annual meeting in Chicago — focused on people whose breast cancers are fueled by estrogen. The most effective treatment for that type of advanced disease includes drugs designed to target specific proteins in breast cancer cells. If those proteins mutate, the drugs stop working, and it’s only a matter of time before the cancer begins growing again.
By detecting these mutations, liquid biopsies serve as an early warning system that people need a different medication, said Dr. Nicholas Turner, study co-author and a professor of molecular oncology at the Institute of Cancer Research and The Royal Marsden hospital in the United Kingdom.
In the new study, people who changed their treatment based on liquid biopsy results were twice as likely to have their tumors controlled than study participants who didn’t change therapy.
Turner said the approach offers a significant improvement compared with current practice.
Currently, doctors look for signs that a cancer treatment is no longer working by performing imaging tests, such as CT scans or PET scans, every three months. These scans allow doctors to see whether tumors are getting bigger.
The study found that liquid biopsies can detect mutations up to nine months before the changes would have become apparent on scans, Turner said. That gives people the opportunity to abandon ineffective treatments as early as possible and switch to ones with better chances of controlling the cancer.
In about 1 in 10 people in the study, liquid biopsies found that their cancer had developed mutations that would make their current treatment less effective.
“We have very effective treatments, but they can wear off,” Turner said. “And if they wear off and the cancer starts growing again, it can make the person unwell. If they have cancer in the bones, it can start to cause pain.”
Researchers randomly assigned half of the 315 people with mutations to change therapy right away and the other half to continue their medications as usual, said Dr. Massimo Cristofanilli, an author of the study and director of breast medical oncology at Weill Cornell Medicine and NewYork-Presbyterian Hospital. One percent of study participants were men.
For the people who changed therapy early, researchers replaced a hormonal drug they had been taking with an experimental cancer drug called camizestrant, which isn’t yet approved by the Food and Drug Administration. Camizestrant interferes with estrogen’s ability to stimulate cancer growth. AstraZeneca funded the clinical trial, which was built on early, basic research funded by the National Institutes of Health, Cristofanilli said.
In study participants who switched to camizestrant, their cancers remained stable — without significant tumor growth — for 16 months, compared with nine months for people who didn’t switch medications, according to the study.
After one year, 61% of study participants who switched to camizestrant had stable disease, compared with 33% of those who didn’t change treatment, according to the study. After two years, 30% of people who switched still had stable disease, compared with 5% who didn’t.
Study participants who switched therapies reported good overall health and quality of life for 23 months, compared with others in the study, who reported a deterioration in health and quality of life after 6.4 months.