Metastatic breast cancer in the lungs refers to cancer that originally developed inside the breast tissue but has spread to the lungs.

Breast cancer can spread to various parts of the body. This is called metastasis. The most common sites for breast cancer metastases include the bones, brain, lungs, and liver.

This article will discuss metastatic breast cancer in the lungs, including its symptoms, diagnosis, treatment options, and outlook or prognosis.

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Doctors refer to metastatic breast cancer as stage 4 breast cancer.

Metastatic is a term that refers to cancer that has spread outside of the original area to a different place in the body. Metastatic breast cancer in the lungs refers to cancer that originally developed inside the breast tissue but has spread to the lungs.

Breast cancer is the most common form of cancer among women. Around 6–10 percent of initial breast cancers that a doctor diagnoses are metastatic. This number does not include breast cancers that progress to stage 4 after the initial diagnosis. Typically, oncologists call metastatic breast cancer stage 4 breast cancer.

Some of these metastatic breast cancer cells may affect the lungs. It is essential that an oncologist confirms that the tumor in the lungs is secondary, meaning that it contains breast cancer cells. If there are no breast cancer cells present, the tumor could be a newly developed primary cancer.

People may not experience symptoms of metastatic breast cancer in the lungs immediately. If symptoms do appear, they can resemble those of a cold or flu.

Symptoms of metastatic breast cancer in the lungs include:

  • a constant cough
  • pain in the lung
  • difficulty breathing or shortness of breath
  • wheezing
  • fatigue
  • recurring infections in the chest
  • coughing up blood
  • loss of appetite
  • unintentional weight loss

As the cancer cells divide and multiply, the primary tumor grows larger. As the primary tumor grows, cancer cells can break off from the primary tumor. These rogue cancer cells can then enter the bloodstream or the lymph system. From there, the cancer cells can travel to distant areas of the body.

In some cases, small amounts of breast cancer cells can survive initial treatment and remain inactive in the body for some time before growing again in primary site or spreading to another area of the body. Doctors call this recurrent, or recurring, breast cancer.

Breast cancer cells must undergo significant changes to survive and grow in the lungs. These cells must also change to withstand attacks from the body's immune system. The treatment options for the newly formed cancer will depend on how it has altered during metastasis.

It is not unusual for cancer to metastasize to multiple sites at once.

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Healthcare providers will often order an imaging test if they suspect lung metastasis.

Diagnosing metastatic breast cancer in the lungs begins with a physical examination and blood tests.

If a health care provider suspects lung metastasis, they will likely order an imaging test, such as:

If a doctor does find a tumor in the lung, their next task involves confirming that the tumor is metastatic breast cancer and not primary lung cancer. This is especially important for people who have smoked or currently smoke.

Other diagnostic procedures that can help confirm a metastatic breast cancer diagnosis include:

  • testing a mucus sample
  • bronchoscopy, where a doctor inserts a flexible camera thread through the nose and into the lungs to examine the respiratory structures
  • needle biopsy of the lung, where a doctor removes a sample of lung tissue for further testing

After someone has received initial treatment, breast cancer can lay dormant in the body before spreading to other areas. People who have received treatment in the past should monitor themselves for any signs or symptoms that could indicate cancer recurrence.

While there is no single way to avoid developing metastatic breast cancer entirely, there are some lifestyle changes that can help reduce a person's risk.

People may reduce the risk of metastases with the following factors:

  • having regular health screenings
  • having regular breast cancer screenings
  • eating a balanced diet
  • exercising regularly
  • not smoking or quitting smoking
  • avoiding excessive alcohol intake
  • maintaining a healthy body weight
  • monitoring vitamin D levels
  • reducing stress

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Although metastatic breast cancer is not curable, chemotherapy can weaken the cancer and stop it growing.

Doctors consider metastatic breast cancer to be a stage 4 cancer. It is not curable, and treatments focus on weakening the cancer to stop it from growing while working to improve the quality of life for the individual.

Treatments for metastatic breast cancer in the lungs usually involve systemic, or body-wide, medications that treat cancer throughout the body, such as the following:

Chemotherapy. Chemotherapy is a drug therapy that destroys all fast-growing cells in the body, both cancerous and healthy.

Hormonal therapy. Hormonal therapy is a cancer treatment that controls cancer cell growth by lowering the levels of certain hormones the cancer needs to grow. Hormone receptor-positive breast cancers respond well to this treatment.

Targeted therapy. This form of cancer treatment attempts to treat cancer with more precision than chemotherapy. These treatments target specific receptors, proteins, or molecules on cancer cells that either make it easier for the body's immune system to identify and destroy cancerous cells or reduce their growth.

Radiation. In the case of metastatic breast cancer, doctors often use radiation therapy to reduce symptoms and control the cancer's growth. Radiation therapy can help reduce pain and lower the risk of broken bones weakened due to cancer.

Metastatic breast cancer in the lungs can cause other health complications that impact a person's overall health and wellbeing.

Fluid in the chest

Breast cancer cells can form in the region between the outside of the lungs and the chest wall, also known as the pleural space. This can cause a build-up of excess fluid, a condition known as a malignant pleural effusion.

Malignant pleural effusions can worsen some of the symptoms of cancer in the lungs, including:

  • a worsening cough
  • shortness of breath or wheezing
  • pain in the chest

Doctors treat malignant pleural effusions by either draining the excess fluid or by carrying out a procedure known as pleurodesis. This involves closing the space between the lungs and the chest wall, which prevents fluid from building up between the two linings.

Toxicity due to treatment

Cancer treatments can cause significant side effects that impact a person's overall health and quality of life. Chemotherapy and other systemic cancer treatments can cause a wide range of symptoms, such as:

  • a lowered immune system function
  • infection
  • fatigue
  • loss of appetite
  • nausea
  • vomiting
  • constipation

Psychological impact

Receiving a diagnosis of stage 4 cancer can leave lasting psychological impacts. People can experience depression, anxiety, and stress as a result of their condition.

People who are struggling with negative psychological symptoms might want to consider joining a support group or seeking professional counseling to help them cope with their situation. Reaching out to friends or loved ones can make a significant difference.

Metastatic breast cancer is the most advanced form. Metastatic breast cancer is not curable, so treatment options focus on weakening the tumor and preventing further growth. While some may view this as a less aggressive approach, controlling the cancer is still a positive outcome.

According to the World Health Organization, breast cancer affects an estimated 2.1 million women each year and accounted for 15 percent of all cancer deaths among women in 2018.

Experts calculate cancer prognoses using a 5-year survival rate, which is the percentage of people who survive for at least 5 years after diagnosis. These are estimates, and actual survival varies depending on a person's characteristics.

The 5-year survival rates for women with breast cancer depends on the stage:

  • stage 0 and 1 is close to 100 percent
  • stage 2, about 93 percent
  • stage 3, about 72 percent, and treatment is often successful
  • stage 4, or metastatic breast cancer, about 22 percent

These statistics do not predict what will happen for any individual, and there are many treatment options for people with metastatic breast cancer.

The long-term outlook for people who have metastatic breast cancer in the lungs depends on many variables. These include:

  • age
  • overall health status
  • how the tumor responds to treatment
  • the size of the primary and secondary tumors
  • whether or not the primary cancer has metastasized to multiple sites within the body