A groundbreaking study suggests that liquid biopsies, a non-invasive blood tests may significantly enhance the care of people with metastatic breast cancer, especially those whose tumors are driven by estrogen. The findings indicate that liquid biopsies can detect changes in cancer cells months earlier than traditional imaging methods, allowing for timely treatment adjustments and potentially prolonged disease control.

Liquid biopsies are highly sensitive blood tests that detect small fragments of tumor DNA or circulating cancer cells in the bloodstream. Unlike conventional imaging or tissue biopsies, these tests are non-invasive and can reveal genetic mutations in cancer cells even before symptoms appear or tumors enlarge. While Liquid biopsies have not yet replaced standard screening methods like mammograms or colonoscopies, their role in advanced cancer management is growing.

The new research, published in The New England Journal of Medicine and presented at the American Society of Clinical Oncology (ASCO) annual meeting in Chicago, focused on people with metastatic breast cancer fueled by estrogen. This form of cancer is typically treated with drugs that target specific estrogen-related proteins. However, when these proteins mutate, current treatments may stop working, causing the cancer to progress.

Dr. Nicholas Turner, co-author of the study and a professor of molecular oncology at the Institute of Cancer Research and The Royal Marsden Hospital in the UK, emphasized the significance of early detection through liquid biopsies. “By identifying mutations early, we can switch patients to a more effective treatment before their cancer worsens,” he said.

Oncologists monitor treatment effectiveness through imaging scans like CT or PET every three months. These scans help determine whether tumours are shrinking or growing. However, Turner’s team found that liquid biopsies could detect key mutations up to nine months before they would be visible on scans. This offers a critical opportunity to replace ineffective treatments sooner.

In the study, 315 patients with estrogen-driven metastatic breast cancer were enrolled. All had developed mutations that could compromise their current therapies. Researchers randomly assigned half to immediately switch treatments based on liquid biopsies results while the other half continued their usual regimen.

Among those who changed therapy early, their hormonal medication was replaced with camizestrant, an experimental drug not yet approved by the FDA—camizestrant works by blocking estrogen’s ability to fuel cancer growth. The trial was funded by AstraZeneca and supported by early research from the U.S. National Institutes of Health, according to co-author Dr. Massimo Cristofanilli, director of breast medical oncology at Weill Cornell Medicine and NewYork-Presbyterian Hospital.

Results showed that participants who switched to camizestrant had a median progression-free survival of 16 months, compared to 9 months in those who stayed on their previous medication. After one year, 61% of early-switch patients still had stable disease, versus only 33% of those who didn’t change therapy. At the two-year mark, 30% of early-switch participants remained stable, compared to just 5% in the delayed group.

Beyond controlling tumor growth, those who changed therapies earlier also reported better overall health and quality of life for up to 23 months. In contrast, participants who remained on their initial medications reported declines in health and well-being after just 6.4 months.

Dr. Turner noted, “If we switch treatment at just the right time, we can keep the cancer asleep and the person well. Many of my patients can continue working and enjoy life with their families.”

While camizestrant was associated with more side effects than standard hormonal therapy, it was generally well tolerated. Only 1.3% of patients discontinued camizestrant due to adverse effects, compared to 1.9% in the standard drug group.

Side effects included reduced white blood cell counts, a slower heart rate, and visual disturbances like flashes or floaters. Despite this, the majority of participants continued using the drug.

Although camizestrant is still under investigation, the FDA has already approved a similar drug called Faslodex, offering another option for patients needing a change in treatment.