metastatic breast cancer
Signs that breast cancer has spread include constant fatigue, constant nausea, loss of appetite and unexplained weight loss

Metastatic breast cancer is stage IV cancer, which has spread to other parts of the body. Cancers are a group of diseases in which some types of cells turn abnormal and proliferate without control. Cancer can start anywhere and spread to any part of the body, but is named by the organ in which it first develops. Men can also develop breast cancer, although it is rare.

If breast cancer spreads to the bone, it is still considered metastatic breast cancer that has spread to the bone; it is not considered to be bone cancer. In metastatic breast cancer, breast cancer cells break from the primary tumor, travel through blood or lymph fluid, settle into other parts of the body and start growing into new metastatic breast tumors.

What are the signs of metastatic breast cancer?

General signs that breast cancer has spread to other organs and become metastatic include the following:

Other symptoms of metastatic breast cancer depend on the specific organ to which it has metastasized. Following are some of the possible symptoms related to the organ that is affected:

Bones

Lungs

Liver

Brain

Skin

What type of breast cancer is most likely to metastasize?

Breast cancers are classified by the types of cells in which they develop. The primary types of cancers that metastasize are invasive cancers which grow large quickly and spread into nearby breast tissue. The two main types of invasive cancers are:

  • Invasive ductal carcinoma (IDC): IDC starts in the ducts and accounts for 80% of invasive breast cancers. 
  • Invasive lobular carcinoma (ILC): ILC starts in the milk glands (lobules) and accounts for 10% of invasive breast cancers.

Breast cancers are also graded from one to three, based on how abnormal the cancer cells look and how fast they grow. Grade one is a low grade cancer that grows slowly and unlikely to spread, and grade three is a high grade cancer that grows fast and more likely to metastasize.

The types of breast cancers that are most likely to metastasize include the following:

  • HER2-positive breast cancer: HER2 breast cancers are aggressive cancers which have an abnormal amount of HER2 proteins on the cell surface. Human epidermal growth factor receptor-2 (HER2) protein regulates cell growth and division, and excess HER2 protein in the cancer cells speed up their growth.
  • Triple negative breast cancer: Triple negative cancers have no HER2 proteins and they also lack hormone (estrogen and progesterone) receptors on them. Hormone receptors (HR) are proteins found on cancer cells which grow in response to hormones. HR cancers respond to hormone therapy and tend to grow slower, but triple negative cancers do not respond to HR-/HER2-positive treatments and grow rapidly.
  • Inflammatory breast cancer: inflammatory breast cancer produces inflammatory symptoms such as swelling and redness, and is caused by cancer cells blocking the lymphatic ducts. Inflammatory breast cancers are usually diagnosed in the third stage when they have already metastasized to the skin.

Some other rare types of breast cancer that grow aggressively include:

  • Metaplastic carcinoma: A type of cancer with cells that can transform into different types of cells
  • Micropapillary carcinoma: An aggressive subtype of invasive ductal carcinoma
  • Mixed carcinoma: The cancer cells have features of both ductal and lobular carcinomas

QUESTION

A lump in the breast is almost always cancer. See Answer

Is metastatic breast cancer curable?

Metastatic breast cancer is not curable, but can be treated to slow the growth of cancer, provide symptomatic relief, prolong life and improve quality of life. Treatment for metastatic cancer is lifelong, however, some patients do opt to forego treatment, except for palliative care.

What is the treatment for metastatic breast cancer?

The primary treatments for metastatic breast cancers are systemic therapies with medications. Medications may vary depending on the type of breast cancer and where it has spread. Medications may be administered as oral tablets, injections or infusions.

Breast cancer patients also have the option of registering for clinical trials for new treatments. Surgery and/or radiation therapy have limited use in treating metastatic breast cancer. Radiation therapy is the use of high energy rays or particles directed at the cancer cells to destroy them.

Surgery and/or radiation therapy may be used in metastatic breast cancer to:

  • Remove the primary tumor in the breast if it is causing an open wound
  • Treat small areas of the brain in case of brain metastasis
  • Relieve pressure on the spinal cord in case of metastasis to the spine
  • Prevent fractures in bone metastasis
  • Treat blockage in the liver
  • Provide relief from pain and other symptoms from metastatic cancer

Systemic therapies for metastatic cancer typically consist of a combination of two or more of the following therapies:

Chemotherapy

Chemotherapy is the primary treatment for metastatic breast cancer. Chemotherapy drugs kill all cells that are in the growth and division phases, including healthy ones. Chemotherapy is particularly toxic to cancer cells because they are always growing and dividing.

Hormone therapy

Hormone therapy may be used in addition to chemotherapy, to shrink tumors or slow down growth in metastatic cancers that are hormone receptor (HR) positive. Hormone therapy may be given as long as it proves useful to the patient without unacceptable side effects.

Targeted therapy

Targeted therapy medications target specific proteins and cell signaling enzymes which promote growth and division in cancer cells. Targeted therapy medications do not directly destroy cancer cells but alter the way they function and slow down tumor growth.

Several different targeted therapy medications are used to treat metastatic breast cancer depending on HR and HER2 status, and gene mutations which play a role in cell growth and division. Types of metastatic breast cancers that are treated with targeted therapy include:

  • HER2 positive cancers
  • HER2 negative cancers with BRCA or PIK3CA gene mutations
  • Triple negative cancers

Immunotherapy

Immunotherapy drugs enhance the ability of immune cells (T-cells) to identify and kill cancer cells. Immunotherapy drugs block the activity of a protein known as PD-1 in T-cells which normally prevents the T-cells from attacking the body’s own cells.

Immunotherapy also works by blocking PD-L1, a protein present in some cancers, which interact with PD-1 in T-cells to escape being killed. Immunotherapy is used to treat triple negative cancers that are positive for PD-L1 protein.

What is the survival rate for metastatic breast cancers?

Breast cancer is the second most common reason for death from cancer in women. Approximately 6% of breast cancers are metastatic at the time of diagnosis and nearly 30% cancers that are in early stages at diagnosis become metastatic. The five-year survival rates for metastatic breast cancer is 28% for women and 22% for men.

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Medically Reviewed on 4/26/2021
References
https://emedicine.medscape.com/article/1947145-overview

https://www.cancercenter.com/cancer-types/breast-cancer/types/rare-breast-cancer-types/metastatic-breast-cancer

https://www.cancer.org/cancer/breast-cancer/treatment/treatment-of-breast-cancer-by-stage/treatment-of-stage-iv-advanced-breast-cancer.html

https://breastcancernow.org/information-support/facing-breast-cancer/secondary-metastatic-breast-cancer/secondary-breast-cancer-symptoms

https://www.cancer.net/cancer-types/breast-cancer-metastatic/statistics#:~:text=Six%20percent%20(6%25)%20of,death%20from%20cancer%20in%20women

https://www.breastcancer.org/symptoms/types/recur_metast#:~:text=Nearly%2030%25%20of%20women%20diagnosed,another%20part%20of%20the%20body