What Is Advanced Breast Cancer?

Reviewed by: HU Medical Review Board | Last reviewed: December 2018

Breast cancer is a condition in which cells in the breast tissue change and begin to grow out of control. Advanced breast cancer (ABC) encompasses both locally advanced breast cancer and metastatic breast cancer.1

What is locally advanced breast cancer?

Depending upon the specific reference, locally advanced breast cancer (LABC) includes:2,3

  • Large breast cancer tumors (more than 5 centimeters [cm] in diameter)
  • Breast cancers of any size that involve the skin of the breast or the underlying muscles of the chest
  • Breast cancers that have spread to multiple local lymph nodes (those located in the arm pit or in the soft tissues above & below the collarbone)
  • Inflammatory breast cancer

LABC are further classified as “operable” or “inoperable,” based on the likelihood that surgery could remove all the cancerous tissue with a clear margin of healthy tissue around the tumor.

One distinguishing characteristic of LABC is that there are not distant metastases, meaning the cancer has not spread to other parts of the body. It is estimated that approximately 10–15 percent of all new breast cancer diagnoses are LABC.2,3

What is metastatic breast cancer?

Metastatic breast cancer (MBC) is when cancer has spread beyond the breast tissue to other areas of the body. When breast cancer spreads to other organs, it commonly spreads to the lungs, the bones, the liver, and/or the brain. However, it can also potentially spread to other parts of the body.

Despite where cancer may spread, it is still considered breast cancer, as the cancer is named for where it originated.4

It is estimated that between 5–10 percent of women with breast cancer have MBC when they are diagnosed. MBC may also occur as a recurrence of breast cancer, which may be years after the original diagnosis.5,6

How does metastatic breast cancer develop?

All cancers develop at a cellular level. Cells are the building blocks of all the different tissues in the body, and in a healthy state, they grow and divide as needed to maintain the body’s structure and function. As cells age or become damaged, they are replaced by new cells.

Cancers develop when changes occur in the cells that cause them to replicate at high rates and can form tumors. Cancerous tumors can spread into surrounding tissues or break off and spread throughout the body through the bloodstream or lymph system.7

Most breast cancers originate from cells that form the ducts which carry milk to the nipple. These are called ductal carcinomas. Another common form of breast cancer are lobular carcinomas, which begin in the cells that form the glands that produce breast milk.8

How is metastatic breast cancer treated?

Treatment for ABC is similar to other stages of breast cancer and may include one or a combination of treatments such as:

Treatment decisions are based on multiple factors, including if the cancer cells have specific characteristics, the age and menopausal status of the individual, what prior treatments may have been used, the presence and site of any metastases, other health conditions, and the patient’s preference.

Breast cancers are also tested for certain cellular receptors, including human epidermal growth factor receptor 2 (HER2), estrogen receptors, and progesterone receptors.1

Currently, there is no cure for metastatic breast cancer, but some patients can live with MBC for extended periods of time with treatment. In some cases, people live for years with MBC.1