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.

Breast cancer can spread to places in the body such as the bones, lungs, liver, and brain. No matter where it spreads, it’s still considered breast cancer and is treated as such.

In some cases, initial treatment for earlier stage breast cancer doesn’t eliminate all cancer cells. There can still be microscopic cancer cells, 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 people live for many years after a diagnosis of stage 4 breast cancer.

This article explains what occurs when breast cancer metastasizes to the lungs.

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 tissues.

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, they can travel through the body and land in distant organs or tissues.

Once cancer cells reach the lungs, they can 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 typically begins 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 its quality.

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 effectively kill cancer cells anywhere in the body. This treatment can help shrink tumors and prevent new tumors from forming.

Chemotherapy is usually the only treatment option for triple-negative metastatic breast cancer, including hormone receptor-negative and human epidermal growth factor receptor 2-negative (HER2-negative) cancers. Chemotherapy is also used 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

People 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 a class called aromatase inhibitors.

Doctors may also prescribe other drugs, such as palbociclib and fulvestrant, for people with estrogen-positive, HER2-negative disease.

Targeted therapies for HER2-positive breast cancer

Targeted therapies can treat HER2-positive breast cancer, 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. The following may help:

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

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

Each treatment 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. Ask your doctor for more information if you’d like to participate in a clinical trial.

You can’t control all risk factors for breast cancer, like genetic mutations, sex, and age. But there are some things you can do to reduce your risk of developing breast cancer.

These include:

  • getting regular physical activity
  • drinking alcohol in moderation, if you drink
  • eating a nutrient-dense diet
  • managing your weight
  • 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.

It’s important to remember there’s no one-size-fits-all treatment for metastatic cancer. You can choose treatments specific to your needs by working closely with your healthcare team.

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

National and regional organizations can assist you with your daily needs, such as household chores, transportation to treatment, or expenses.

According to the American Cancer Society, the 5-year relative survival rate for metastatic breast cancer is 31%. This is only an estimate. The outlook for people with metastatic breast cancer continues to improve as treatments are refined.

Metastatic breast cancer is when the cancer spreads to other parts of the body, such as the lungs, bones, or the brain. In many cases, treatment for local breast cancer may not eliminate all cancer cells, and microscopic cancer cells left behind can ultimately end up spreading.

Although there’s no cure for metastatic breast cancer, there are many treatments that can ease symptoms and prolong life, such as chemotherapy, medication, and radiation.

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