Metastatic Breast Cancer Facts and Statistics: What You Need to Know

Each year, more than 290,000 people are diagnosed with breast cancer in the United States. At diagnosis, about 6% of females have metastatic breast cancer, or cancer that has spread to other areas of the body. Others go on to develop metastatic breast cancer when cancer recurs.

Breast cancer is the second most common cause of cancer deaths in women in the United States. Metastatic breast cancer causes most of the deaths from breast cancer. This article will highlight important facts and statistics you should know about metastatic breast cancer.

Metastatic Breast Cancer Overview

Metastatic breast cancer is also called stage 4 breast cancer. It is breast cancer that has spread to distant parts of the body or to other organs. For instance, breast cancer that has spread to the bones is not bone cancer, but metastatic breast cancer. The most common areas for breast cancer to spread are the bones, brain, lungs, or liver.

Metastatic breast cancer that is initially diagnosed as such is called de novo metastatic breast cancer. Breast cancer that recurs and has spread is called recurrent metastatic breast cancer. Metastatic breast cancer is different than locally advanced breast cancer, which is breast cancer that has spread to nearby lymph nodes or tissues.

Statistics specifically for metastatic breast cancer often are not collected. This is because the majority of statistics concerning breast cancer do not differentiate between metastatic breast cancer and nonmetastatic breast cancer.

It can be difficult to get accurate statistics and figures for many topics in this kind of cancer. When statistics are collected, they are often for de novo metastatic breast cancer and not recurrent.

How Common Is Metastatic Breast Cancer?

Approximately 6 out of 100 people with breast cancer have metastatic breast cancer at diagnosis. Most commonly, metastatic breast cancer occurs months to years after an individual is treated for nonmetastatic breast cancer. This can also be called a distant recurrence.

It's estimated that 10% to 52% of people initially diagnosed with local and regional stages of breast cancer will eventually develop metastatic breast cancer.

Metastatic Breast Cancer by Ethnicity

Non-Hispanic Black individuals are more likely to present with de novo metastatic breast cancer (9%) than non-Hispanic White individuals (6%) or Hispanic individuals (6%).

Underuse of appropriate treatment has been found more in Black women (34%) and Hispanic women (23%) than White women (16%). The disparities in health care and treatment contribute to late diagnosis, undertreatment, and, eventually, discrepancies in mortality.

Metastatic Breast Cancer by Age and Gender

While the median age of breast cancer diagnosis in women is 61, metastatic breast cancer can occur at any age. When it occurs in younger women, it tends to present with more aggressive clinical features like a larger tumor and more lymph node involvement. Younger and middle-aged people tend to have more metastases than older people.

Male breast cancer, in general, is rare, making up about 1% of all malignant cancers in men. It is the cause of less than 0.5% of all cancer deaths in men each year. These low numbers make studying breast cancer in men more challenging, and because of this, treatment recommendations are often taken from studies on women.

Although studies on male metastatic breast cancer are ongoing, until there are better data, it has been determined that treatment guidelines should remain as is.

Causes of Metastatic Breast Cancer and Risk Factors

Metastatic breast cancer is caused by cancer cells that break off from the main tumor (primary tumor) and get into the bloodstream or the lymph system. The cancer cells then travel in these fluids and can settle in an organ or part of the body, growing new tumors.

Any kind or stage of breast cancer can metastasize. It’s not possible to know or predict which ones will and which ones won’t. While there’s no definitive way to prevent metastasis from occurring, there are some risk factors that may impact whether breast cancer metastasizes, including:

• Type of breast cancer, like whether it’s hormone receptor-positive or human epidermal growth factor receptor 2 (HER2)-positive, if it’s triple-negative breast cancer, etc.
• Whether it’s a fast- or slow-growing cancer
• Characteristics of the cancer when first diagnosed, such as stage, tumor size, lymph node status

It’s also important to remember that everyone is different. Some people with many risk factors will never have their cancer metastasize, whereas someone with very early breast cancer may later have it recur and metastasize.

What Are the Mortality Rates for Metastatic Breast Cancer?

While metastatic breast cancer is not curable, it is treatable. Treatments can help extend one’s life and help control the spread of cancer and minimize symptoms. The five-year survival rate for women with metastatic breast cancer is 29%. For men, it is 22%.

Treatments are becoming more focused and targeted. These statistics should be taken as general information, not as a statement of a prognosis (expected outcome) for an individual.

Screening and Early Detection

Regular screening for breast cancer and early detection can help improve survival rates. However, since many instances of metastatic breast cancer occur after treatment for nonmetastatic breast cancer, this is not always possible. Screening tests used can include:

• Mammogram: Uses X-rays
• Breast magnetic resonance imaging (MRI): Uses magnetic fields
• Clinical breast exam
• Breast self-exam

It’s also important to remember that these tests do not screen for or detect metastatic breast cancer. If metastases are suspected, other tests may be done, including:

• Chest X-ray
• Bone scan: Uses a radioactive tracer to look for bone damage
• Ultrasound of the liver: Uses sound waves
• Positron emission tomography (PET) scan: Uses a short-acting radioactive tracer to look for active cells
• Computed tomography (CT) scan: Uses X-rays and a computer

Summary

Metastatic breast cancer is breast cancer that has spread to distant organs or areas of the body. It is not curable, but it is treatable. Various factors impact diagnosis and survival, including age, ethnicity and race, and clinical characteristics of the initial cancer diagnosis.

Better and more targeted treatments are being developed regularly, so improvements in long-term survival are possible.