The chance of survival from breast cancer has dramatically increased in recent years, partly thanks to better screening programs and awareness of the disease, meaning more women are diagnosed at an earlier stage.
However, women who have tumors which have spread to other organs (metastatic breast cancers) only have a five-year survival rate of 22%.
A new study published today in the journal Nature Cell Biology has uncovered a new way by which these disseminated tumor cells (DTCs) may hide in other parts of the body, evading therapy designed to eliminate them before they can grow into metastatic tumors.
DTCs can be found in any part of the body in breast cancer patients, but an estimated 70% of women with metastatic breast cancer have tumors in their bones, thought to arise from DTCs that have planted themselves in the bone marrow, the spongy, blood cell factories present in large bones in the body such as the hip and leg bones.
"We know regardless of where we look we find dormant breast cancer cells around blood vessels. DTCs in bone marrow break down bone by chewing holes they can grow into," said Dr Cyrus Ghajar, director of the Laboratory for the Study of Metastatic Microenvironments at Fred Hutchinson Cancer Research Center in Seattle and lead author of the study.
The bone marrow has an extensive network of blood vessels to facilitate the constant production and expulsion of new blood cells.
When the researchers looked in more detail as to why the DTCs were there, they found that the DTCs were being effectively stuck to the blood vessels by proteins called integrins, which stick out on the surface of cells, allowing them to communicate with the external environment.