In an outstanding breakthrough, an international team of scientists has discovered a protein biomarker than can predict whether a patient's metastasized breast cancer is dormant or about to turn deadly. The research will not only help doctors better treat patients suffering from breast cancer, but also points to new treatments that may be able to stimulate dormancy in cancer cells before they metastasize.

Breast cancer is still the most frequently appearing cancer seen in women, and while it can be treated effectively if caught early, it is also incredibly deadly if it is allowed to metastasize. Bone marrow is the most common first metastatic point in the spread of breast cancer.

Doctors can currently test a patient's bone marrow for residual disseminated tumor cells (DTCs), but these markers are not the most reliable signifier of how active the disease is. Around 60 percent of patients with identifiable DTCs have been found to remain relapse-free for up to five years or more.

The new study set out to investigate what could be causing these metastatic DTCs to lie dormant for many years. The exciting revelation was that a specific protein, called NR2F1, seemed to be the key to modulating the activity of cancer cells. When a high volume of NR2F1 was found in the bone marrow cancer cells, the patients lived longer and the cancer remained dormant, but if no, or very little, NR2F1 was found in the metastasized cancer cells then the cancer spread faster and the patient died sooner.

"This research shows that the survival advantage in these patients is due to high levels of this protein," says lead researcher Julio Aguirre-Ghiso. "Tests using this protein marker could further improve curative treatment of breast cancer, sparing patients from unnecessary treatments. Identifying patients with disseminated disease that is not yet symptomatic and characterizing it for potential dormancy or metastatic recurrence is a game changer."

The benefits of being able to effectively identify patients with more or less aggressive metastatic characteristics simply through a bone marrow test are undeniably significant. But, perhaps ever more exciting, is the potential for harnessing this process and inducing dormancy. Other studies targeting prostate cancer have already revealed that increasing levels of NR2F1 may induce dormancy in that cancer, and research is already underway into drugs that can upregulate NR2F1 to potentially stifle cancer metastasis.

"This opens the way for testing new treatments that prevent metastasis by inducing dormancy or eradicating the dormant disseminated cancer cells that have not yet initiated metastatic growth," says Aguirre-Ghiso on possible future research directions.

In the short term though, this biomarker discovery can rapidly assist doctors in evaluating the potential aggressiveness of breast cancer once it has metastasized to the bone. While metastatic breast cancer currently has no effective cure, this discovery is an exciting step towards better managing the disease.

The story is published in the journal Breast Cancer Research.