Metastatic breast cancer, also known as stage 4 or advanced breast cancer, is diagnosed when cancer has spread from the breast and lymph nodes to other parts of the body. (Cancer stages are sometimes noted with Roman numerals — in this case, stage IV.) Once cancer has metastasized — spread — it becomes more difficult to treat, which can affect life expectancy.
Your prognosis (outlook) with MBC is determined by many factors, including your age, the type of breast cancer you have, where it has spread, and the number of distant metastases. Your oncologist (doctor who specializes in diagnosing and treating cancer) can help you better understand your personal factors that affect your outlook with MBC.
The National Cancer Institute defines survival rate as “the percentage of people in a study or treatment group who are still alive for a certain period of time after they were diagnosed with or started treatment for a disease, such as cancer.” Researchers typically refer to a five-year survival rate — how many people with the condition are living five years after initial diagnosis or beginning treatment.
According to the American Cancer Society, the five-year relative survival rate (comparing people who have the same type and stage of breast cancer to the general population) for metastatic breast cancer is 30 percent. This means that five years after being diagnosed with MBC, 30 percent of people are likely not to have died of breast cancer. It’s important to note that this statistic is based on data from 2012 to 2018. Treatments continue to improve and lengthen the life span of those living with MBC.
While metastatic breast cancer can be treated, there is currently no cure. Instead, treatments aim to extend life span by preventing your cancer from progressing (getting worse or spreading more). The goal of MBC treatment is to keep your cancer stable for as long as possible. Cancer treatment can also focus on improving day-to-day quality of life.
Most clinical trials (research studies on treatments involving humans) that look at new MBC therapies use progression-free survival to measure how well a treatment is working. Progression-free survival measures the amount of time (typically in months) until, after you start a treatment, your cancer worsens or spreads. The longer the progression-free survival, the better a treatment keeps cancer in check.
Researchers also use overall survival to measure the length of time that participants are still alive after beginning a treatment. Overall survival is usually given in months to show a drug’s effectiveness. The longer the overall survival, the better a treatment keeps people alive for longer.
Overall survival statistics have continued to improve over the years as new MBC treatments have become available. Median overall survival measures the length of time that 50 percent of people with MBC remain alive. Studies show that between 1990 and 2010, the median overall survival increased from 21 months to 38 months. This means that over the course of 20 years, new treatment options helped nearly half of people with metastatic breast cancer live 17 months longer.
Each person’s MBC is unique, and certain factors can affect your outlook with the disease. These include your age, your type of breast cancer, and where it has spread in your body. When determining your prognosis, your oncologist will take these factors into consideration.
Studies show that your age at metastatic breast cancer diagnosis can affect your prognosis. Younger age (40 or under) is associated with a better outlook with MBC, especially in people with hormone receptor (HR)-positive and human epidermal growth factor receptor 2 (HER2)-positive subtypes.
Interestingly, this group also tends to have more aggressive features, including more metastases to the liver and lungs. Even so, people diagnosed at a younger age have a better outlook than those who are older.
Breast cancer is broken down into different molecular subtypes, which are based on the proteins found in cancer cells. These proteins are called hormone receptors — including estrogen receptor (ER) and progesterone receptor (PR) — and their presence or absence can affect the prognosis of metastatic breast cancer.
For example, the life expectancy for triple-negative metastatic breast cancer (TNBC, which has no hormone receptors) is shorter than that of other cancers. This is because TNBC grows quickly and tends to relapse (return after a period of improvement) more than other subtypes. The five-year relative survival rate for metastatic TNBC from 2012 to 2018 was 12 percent, according to the American Cancer Society. This means that five years after diagnosis, 12 percent of people are likely not to have died from it.
On the other hand, studies have found that HR-positive metastatic breast cancer is associated with a better outlook than MBC without hormone receptors.
An overexpression (excess) of HER2 — a protein involved in cell growth and division — in breast cancer cells can also tell oncologists about metastatic breast cancer prognosis. People with overexpression (HER2-positive cancer) tend to have a worse outlook than those without overexpression (HER2-negative cancer) of this protein. HER2 can provide an important target for targeted medications.
The primary tumor refers to the first tumor found in your body at diagnosis. Metastatic cancer is caused by the primary tumor spreading to other parts of the body. Cancer research shows that the size of your primary tumor can predict your MBC prognosis. Larger primary tumors are associated with shorter survival.
Breast cancer often spreads to the nearby lymph nodes in the breast tissue before metastasizing. When you’re diagnosed, you may have a lymph node removed to be examined for cancer cells. Studies show that having cancer cells in your lymph nodes at the time of diagnosis is associated with a worse prognosis because your cancer may be more aggressive and likely to spread.
When breast cancer metastasizes, it tends to spread to the bones, liver, lungs, and brain. Researchers have looked into whether the metastatic site affects your outlook with metastatic breast cancer. Research suggests that around 70 percent of people with MBC develop bone metastases, according to the Journal of Surgical Oncology. People whose breast cancer spread to the bone, rather than other areas, also have the most favorable prognosis, with a large 2019 study in BMC Cancer reporting a three-year survival rate of around 50 percent.
In the 2019 study, researchers reported that liver and lung metastases led to three-year survival rates of 38.2 percent and 37.5 percent, respectively. Brain metastases tended to be more aggressive and were associated with a three-year survival rate of around 20 percent.
Many of the factors surrounding your outlook with metastatic breast cancer are due to breast cancer itself, so they’re likely out of your control. The most important steps you can take are to stick with your breast cancer treatment plan and stay healthy in general. Many people with MBC continue to live with it and manage the disease for years after their diagnosis.
Your oncology team will work closely with you to develop the best treatment plan for your MBC. Be sure to attend all your checkups so your health care providers can monitor your progress to see whether your treatments are effective. Your oncologist may also provide you with additional information on building healthy habits to keep you strong during treatment, including:
Your mental health is just as important as your physical health. Be open with your care team if you’re struggling with anxiety or depression. They can connect you with support and help you find ways to manage stress.
MyBCTeam is the social network for people with breast cancer and their loved ones. On MyBCTeam, more than 67,000 members come together to ask questions, give advice, and share their stories with others who understand life with breast cancer.
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