Metastatic breast cancer refers to breast cancer that’s spread beyond the local or regional area of origin to a distant site. It’s also called stage 4 breast cancer.

Although it can spread anywhere, breast cancer spreads to the bones in nearly 70 percent of people with metastatic breast cancer, estimates the Metastatic Breast Cancer Network.

Other common sites are the lungs, liver, and brain. No matter where it spreads, it’s still considered breast cancer and is treated as such. About 6 to 10 percent of breast cancers in the United States are diagnosed at stage 4.

In some cases, initial treatment for earlier stage breast cancer doesn’t eliminate all cancer cells. There can be microscopic cancer cells left behind, allowing the cancer to spread.

Most of the time, metastasis occurs after initial treatment is completed. This is called a recurrence. Recurrence can happen within a few months of finishing treatment or many years later.

There’s no cure for metastatic breast cancer yet, but it’s treatable. Some women will live for many years after a diagnosis of stage 4 breast cancer.

Breast cancer starts in the breast. As the abnormal cells divide and multiply, they form a tumor. As the tumor grows, cancer cells can break away from the primary tumor and travel to distant organs or invade nearby tissue.

Cancer cells can enter the bloodstream or migrate to nearby lymph nodes under the arm or near the collarbone. Once in the blood or lymph systems, cancer cells can travel through your body and land in distant organs or tissue.

Once cancer cells reach the lungs, they can start to form one or more new tumors. It’s possible for breast cancer to spread to multiple locations at the same time.

The signs and symptoms of cancer in the lungs may include:

You may not have noticeable symptoms at first. Even if you do, you may be inclined to dismiss them as symptoms of a cold or flu. If you’ve been treated for breast cancer in the past, don’t ignore these symptoms.

Diagnosis will likely begin with a physical exam, blood work, and a chest X-ray. Other imaging tests may be needed to provide a more detailed view. These exams may include:

A biopsy may also be necessary to help determine if the breast cancer has metastasized to your lungs.

When treating metastatic breast cancer, the goal is to help minimize or eliminate symptoms and lengthen your life without sacrificing your quality of life.

Breast cancer treatment depends on many factors, such as the type of breast cancer, previous treatments, and your overall health. Another important factor is where the cancer has spread and whether the cancer has spread to multiple locations.

Chemotherapy

Chemotherapy can be effective in killing cancer cells anywhere in the body. This treatment can help shrink tumors and stop new tumors from forming.

Chemotherapy is usually the only treatment option for triple-negative metastatic breast cancer (hormone receptor-negative and HER2-negative). Chemotherapy is also used in conjunction with HER2-targeted therapies for HER2-positive breast cancer.

If you’ve previously had chemotherapy, your cancer may have become resistant to those drugs. Trying other chemotherapy drugs may be more effective.

Hormonal therapies

Those with hormone-positive breast cancer will benefit from drugs that block estrogen and progesterone from promoting cancer growth, such as tamoxifen or a drug from the class called aromatase inhibitors.

Other drugs, such as palbociclib and fulvestrant, may also be used for those with estrogen-positive, HER2-negative disease.

Targeted therapies for HER2-positive breast cancer

HER2-positive breast cancer may be treated with targeted therapies such as:

  • trastuzumab
  • pertuzumab
  • ado-trastuzumab emtansine
  • lapatinib

Radiation

Radiation therapy can help destroy cancer cells in a localized area. It may be able to lessen symptoms of breast cancer in the lungs.

Easing symptoms

You may also want treatment to ease symptoms caused by tumors in the lung. You may be able to do this by:

  • draining fluid accumulating around the lung
  • oxygen therapy
  • a stent to unblock your airway
  • pain medication

Various medications are available by prescription to help clear your airways and reduce coughing. Others can help with fatigue, loss of appetite, and pain.

Each of these treatments has potential side effects that vary depending on the person. It’s up to you and your doctor to weigh the pros and cons and decide which treatments will enhance your quality of life.

If side effects begin to impair your quality of life, you can change your treatment plan or choose to stop a particular treatment.

Researchers are studying a variety of potential new treatments, including:

  • poly (ADP-ribose) polymerase (PARP) inhibitors
  • phosphoinositide-3 (PI-3) kinase inhibitors
  • bevacizumab (Avastin)
  • immunotherapy
  • circulating tumor cells and circulating tumor DNA

Clinical trials for treating metastatic breast cancer are ongoing. If you’d like to participate in a clinical trial, ask your doctor for more information.

It’s important to remember there’s no one-size-fits-all treatment for metastatic cancer. By working closely with your healthcare team, you’ll be able to choose treatments specific to your needs.

Many people with metastatic cancer find comfort in support groups where they can talk with others who also have metastatic cancer.

There are also national and regional organizations that can assist you with your daily needs, like household chores, driving you to treatment, or helping with expenses.

For more information about resources, call the American Cancer Society’s 24/7 National Cancer Information Center at 800-227-2345.

According to the American Cancer Society, the five-year survival rate for metastatic breast cancer is about 27 percent. This is only an estimate. The outlook for people with metastatic breast cancer continues to improve as treatments are refined.

Some risk factors, like genetic mutations, gender, and age, can’t be controlled. But there are some things you can do to reduce your risk for developing breast cancer.

These include:

  • engaging in regular exercise
  • drinking alcohol in moderation
  • having a healthy diet
  • avoiding becoming overweight or obese
  • not smoking

If you’ve previously been treated for breast cancer, those lifestyle choices may help reduce the risk of recurrence.

Recommendations for breast cancer screening vary depending on your age and risk factors. Ask your doctor which breast cancer screenings are appropriate for you.

Find support from others who are living with breast cancer. Download Healthline’s free app here.