Researchers at the Hebrew University of Jerusalem and the Weizmann Institute of Science have developed a blood testing method that can detect early-stage breast cancer with 95% accuracy.

The test also helps assess the risk of recurrence after treatment and can identify an increased likelihood of cancer returning even in patients classified as low-risk by conventional methods.

The findings were published in the journal Nature. The research was conducted in collaboration with physicians at Kaplan Medical Center in Rehovot.

Liquid biopsies, which detect traces of tumor cells in the blood, are considered a promising area of oncology. However, at early stages, these traces are present in extremely small amounts, making tumors difficult to detect and increasing the risk of false-positive results.

The new technology is based on studying epigenetic changes—chemical tags that regulate gene activity. If DNA can be compared to a cookbook containing instructions for cells, epigenetic tags are like bookmarks and annotations indicating which instructions should be used and how actively.

When cells, including cancer cells, die, they release nucleosomes—fragments of DNA wrapped around proteins—into the bloodstream. The researchers used technology developed by scientist Efrat Shema's team that employs fluorescent labels and single-molecule microscopy to analyze the epigenetic characteristics of millions of nucleosomes.

First, the scientists studied tumor tissue samples from 12 women scheduled to undergo surgery to remove their tumors. They then identified distinctive epigenetic signatures of the tumors and learned how to detect them in the blood.

To validate the method, the researchers used blood samples from 77 breast cancer patients who had been followed for at least five years at the Mayo Clinic in Florida, as well as from 30 healthy women. Artificial intelligence models were trained to distinguish between samples from the two groups. The accuracy of detecting early-stage cancer, when the tumor remained confined to the breast and measured no more than 2 cm, reached 95%.

During the study, the scientists discovered that even tumors not considered particularly aggressive may contain a small population of cells with an increased ability to invade surrounding tissues. These cells had a distinctive epigenetic profile.

Experiments in laboratory models of breast cancer showed that aggressive cells can arise from initially nonaggressive cells. According to the scientists, the differences between them appear to be largely driven by epigenetic changes, rather than genetic mutations alone.

The researchers suggested that these cells may contribute to recurrence: treatment destroys the bulk of the tumor, but individual cells survive and later give rise to new growth.