Breast cancer: a simple blood test to detect the beginning of a relapse

Detecting, through blood tests, biological traces of a risk of relapse of certain breast cancers and then delivering preventive treatment: this promise seems to be confirmed by new data, a further illustration of the benefits of liquid biopsy.

This technology, also called circulating tumor DNA, involves tracking the progression of cancer through a simple blood test—not a conventional biopsy, which requires much more extensive sampling. The research focuses on the presence of tumor-produced DNA in the blood, a source of valuable genetic information.

This represents a major scientific advance in recent years. And recent data confirms a potentially major application: preventing relapses early and non-invasively for some women with hormone-dependent cancers—the most common type of breast tumor—that have metastasized.

"A new drug," camizestrant (AstraZeneca), but "above all a new concept," are the focus of a plenary session at the 61st congress of the American Society of Clinical Oncology (Asco) in Chicago and of a publication in the New England Journal of Medicine, Professor François-Clément Bidard of the Curie Institute, the last author of the article, emphasized to the press.

Currently, women with hormone-dependent breast cancer at the metastatic stage are generally treated with a combination of drugs: hormone therapy that reduces estrogen production (anti-aromatase) and treatment that inhibits cell proliferation (CDK4/6 inhibitor).

But, for nearly 40% of these patients, a crucial gene for the estrogen receptor (ESR1) mutates, leading to resistance to hormone therapy and, ultimately, cancer recurrence. The promise now is to detect these mutations in the blood several months before they cause the cancer to advance again, to change hormone therapy, combine it with a drug that inhibits the cell cycle, and ultimately reduce the risk of tumor recurrence.

This was already the conclusion, in the fall of 2022, of a French academic trial (Pada-1) led by Professor Bidard. It is now also the conclusion of an international phase III clinical trial (Serena-6) of a new AstraZeneca drug, developed in its wake.

Of nearly 3,000 patients monitored by blood tests every 2-3 months, 315 developed a mutation in the blood, without re-evolution of the cancer, and were divided into two groups: a standard one, which continued its treatment, and an experimental one, which received camizestrant and the cell cycle inhibitor.

Patients receiving this new oral treatment saw their risk of cancer progression reduced by 56%, delaying the time to first recurrence by an average of about 6 months. At 12 months, the progression-free survival rate was 60.7% for patients receiving camizestrant compared to 33.4% for those who did not.

At 24 months, progression-free survival reached 29.7% compared to 5.4%," the Curie Institute detailed in a press release, praising "a revolutionary approach." This marks "a first in breast cancer, (and) can be extrapolated beyond this cancer," Mr. Bidard, a liquid biopsy specialist, told the press.

For the past fifteen years, work on circulating tumor DNA, which can be collected by simple blood tests thanks to advances in molecular biology, has continued to fuel thousands of scientific studies and growing hopes for applications. Scientists are seeking a path toward more personalized and preventative medicine, as well as less invasive ones for cancer patients.

In this case, it is "the first time that the pharmaceutical industry has realized the potential of liquid biopsy to receive approval from health authorities for molecules, which suggests that other manufacturers will rush into this new way of initiating treatments," according to Professor Bidart.

As the number of cases of hormone-dependent breast cancer continues to rise worldwide, competition is also increasing among pharmaceutical companies to develop and profit from next-generation hormone therapies.

AstraZeneca, which is increasingly focusing on anticancer drugs, has positioned camizestrant as a first-line drug. This strategy aims to differentiate itself from several rivals, such as Roche, Pfizer, and Eli Lilly, which are conducting several trials in this therapeutic family.