Breast cancer that has spread to other parts of the body is referred to as metastatic breast cancer. It can be found in organs such as the lungs, liver, or bones. It may have spread when the original tumor broke apart and traveled through the bloodstream or lymphatic system, a network of nodes and vessels. Even though it has spread to a different area of the body, doctors still name the cancer for the area where it started, such as if it is in the lungs, it is called metastatic breast cancer and not lung cancer.
Most of the time, breast cancer metastasizes because the initial treatment did not completely destroy all the cancer cells. It can also happen because the cancer is fast-growing, which makes it more likely to spread. The type of breast cancer that you have plays a role as well. For example, some types of breast cancer, such as HER2-positive and triple negative breast cancers, are more aggressive and tend to spread faster.
The most common types of breast cancer are invasive lobular carcinoma, which start in the lobules, and in ductal carcinoma, which begin in the milk ducts. A smaller percentage of breast cancers start in other locations in the body, including squamous cell carcinoma and hereditary non-polyposis type 2 (HNPT2) breast cancer.
It is estimated that 20% to 30% of patients with early-stage breast cancer will experience a recurrence, meaning their disease will return, after being treated initially. The chances of recurrence are influenced by the size and stage of the original tumor, lymph node involvement, and the underlying biology, including hormone receptor status and HER2 status.
Despite advances in treatment, metastatic breast cancer is still incurable for many patients. But there is good news: The survival of patients living with metastatic breast cancer has improved significantly over the past several decades, thanks to effective treatment in the neoadjuvant and adjuvant settings as well as advances in drug development.
MSK oncologist Chau Dang, MD, explains that patients with metastatic breast cancer have more treatment options than ever before. Some of the most exciting advances include therapies that block the protein HER2 and other targeted treatments with few side effects. Hormone therapies, which target the cancer cells that are sensitive to estrogen, remain an important option for women with hormone-sensitive metastatic breast cancer. There are also clinical trials underway examining new immunotherapies for metastatic breast cancer.
In a recent study, researchers used a large and validated tissue microarray database to identify molecular characteristics of primary invasive breast cancers and to determine the frequency of up to five distant relapse sites for a group of patients. They also identified variables that influence these site-specific relapses, such as intrinsic subtype and patient and tumor characteristics.
BCRF has invested millions of dollars in research into the cause and prevention of metastatic breast cancer, the most advanced form of the disease. We are proud to support several major initiatives in this area, including the creation of an experimental model system and open-access online database of metastatic breast cancer models that can be used by scientists around the world.
