What Is the Survival Rate of Stage 4 (Metastatic) Breast Cancer?

Stage 4 (metastatic) breast cancer has been shown to have a five-year survival rate of 31%. People with earlier-stage breast cancer tend to have a higher five-year survival rate of 99%. Keep in mind that life expectancy depends on several factors, such as the type of cancer, where it's spread, and how well it responds to treatments.

Metastatic breast cancer is an advanced stage of the disease in which cancer cells have spread beyond the breasts and lymph nodes. Cancer cells commonly affect the bones, liver, lungs, and brain.

What Is Metastatic Breast Cancer?

Metastatic breast cancer, which is also known as stage 4 breast cancer, has spread beyond the breast and the surrounding lymph nodes to other body parts. About 20% to 30% of people with breast cancer will develop metastatic breast cancer after an initial earlier-stage diagnosis. Just 6% of people have metastatic breast cancer when they're first diagnosed.

"Basically what's happening is the cancer cells are growing ... they get into the bloodstream which then allows them to travel to distant sites [in the body]," Evelyn Toyin Taiwo, MD, hematologist and oncologist at Weill Cornell Medicine and NewYork-Presbyterian Brooklyn Methodist Hospital, told Health.

Metastatic breast cancer cells can spread anywhere in the body. They most often take up residence in the bones, liver, lungs, and brain. It's unclear how or why certain cancers metastasize and others don't or why breast cancer cells spread to these specific regions.

The type of cancer may play a role in where it spreads. Triple-negative breast cancer, for example, often spreads to the lungs. Estrogen-receptor (ER) positive breast cancer commonly spreads to the bones.

Metastatic Breast Cancer Survival Rates

Metastatic breast cancer is the most advanced stage of breast cancer, and there's no cure for it. The five-year survival rate for people with metastatic breast cancer is 31%. People with this form of breast cancer are just 31% as likely to be alive five years from diagnosis as people who don't have cancer.

This may sound grim, but there are a few important things to keep in mind about survival rates. There's a lot of variability since many factors affect survival rate, such as:

• Age at diagnosis
• How cancer responds to treatment
• Other existing health conditions 
• Type of breast cancer (e.g., triple-negative or HER2-positive)
• Where cancer cells spread in the body (e.g., bones, lungs, liver, brain, or elsewhere), and how extensive it is

The life expectancy for someone with metastatic breast cancer who's been on the same treatment for three years is likely going to be better than if the cancer doesn't respond to treatment. A person who has one bone lesion (cancer site) will similarly fare better than if cancer cells have spread to multiple sites.

Understanding the Prognosis

Official metastatic breast cancer survival rates can be misleading. "The average includes all the people who do worse than the average and all the people who do better," Nancy Lin, MD, an oncologist who specializes in breast cancer at Dana-Farber Cancer Institute in Boston, told Health.

How the survival rate is calculated also matters. Data from the National Cancer Institute's Surveillance, Epidemiology, and End Results Program (SEER) only factors in people with a specific type of metastatic breast cancer.

Dr. Lin often relies on clinical trial data for better estimates since these trials tend to include other types of metastatic breast cancer. This isn't to say that SEER data is bad or inaccurate. SEER plays a critical role in providing experts with data to inform treatment, care, and more.

Survival rates generally tend to be a tad outdated. The good news: "There's been significant progress in terms of survival [from metastatic breast cancer]," said Dr. Taiwo.

A review published in 2018 found that the average life expectancy from metastatic breast cancer increased from 21 months (slightly less than two years) to 38 months (just over three years) between 1990 and 2010. This number has likely improved since then, thanks to improved treatment options.

Treatment Options

Metastatic breast cancer isn't curable. There are still many treatments available to control the disease, help extend a person's life, and improve their quality of life.

Treatments that manage metastatic breast cancer include:

• Chemotherapy, particularly for metastatic triple-negative breast cancer
• Immunotherapy, which helps the immune system target and destroy cancer cells
• Medicines that strengthen the bones
• Radiation therapy to manage pain caused by bone lesions
• Targeted hormone therapy for metastatic hormone-receptor-positive breast cancer (e.g., ER-positive breast cancer)

A Quick Review

The metastatic breast cancer survival rate is lower than that of earlier stages of breast cancer. Remember that several factors can impact life expectancy. It's important to consider the type of cancer, where it's spread, and how well it responds to treatments.

Treatments and care advancements have come a long way to improve the odds significantly. You may feel empowered that there are many treatments out there to manage symptoms and improve your quality of life.