What Is Metastatic Lung Cancer?

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Metastatic lung cancer is the most advanced lung cancer stage where the disease has spread (metastasized) to distant organs. It is sometimes referred to as stage 4 cancer. It can occur with any type of lung cancer,

Although metastatic lung cancer is challenging to treat, newer targeted drugs and immunotherapies are increasing survival times and quality of life in people with this advanced cancer.

Doctor and patient discuss diagnosis

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Types of Metastatic Lung Cancer

There are numerous of types of lung cancer, each of which can metastasize if not treated properly. Some are more likely than others to spread.

Non-small cell lung carcinoma (NSCLC): The most common type of lung cancer. Subtypes include adenocarcinoma, squamous cell carcinoma, and large cell carcinoma. According to the American Cancer Society, 80% to 85% of lung cancers are non-small cell lung carcinomas.

Small cell lung carcinoma (SCLC): Also known as oat cell cancer, this fast growing, highly metastatic type of cancer accounts for 10% to 15% of lung cancers.

Carcinoid tumors: These are very slow-growing neuroendocrine tumors, meaning they affect hormone -producing cells in the lungs. Those classified as typical carcinoids rarely spread beyond the lungs; atypical carcinoid tumors tend to grow a bit faster and are more likely to spread to other organs.

Pleural mesothelioma: A relatively rare type of lung cancer most often caused by exposure to asbestos.

Symptoms

Even after lung cancer reaches an advanced stage, the most common symptoms can be relatively subtle or easily be mistaken for less serious medical issues—so much so that 57% of lung cancers have already metastasized by the time they're diagnosed.Those symptoms include:

As lung cancer spreads, other symptoms can develop depending on the organs affected:

Causes

Lung cancer metastasis occurs when tumor cells break away from where they originally developed and travel to other parts of the body. The process usually begins when the cancer cells invade tissues close to the primary site. From there they can enter nearby lymph nodes and blood vessels and travel to other parts of the body via the lymphatic system or bloodstream.

Along the way, the cancer cells might leave the vessels or lymphatic system or blood vessels and settle into tissues where they continue to grow until another tumor (metastasis) forms. 

Lung cancer most commonly metastasizes in the brain, the second lung, bones, liver, or adrenal glands.

When cancer spreads, it retains the same name as the original cancer. Therefore, lung cancer that spreads to the liver is still called lung cancer. Lung cancer most commonly metastasizes in the brain, the second lung, bones, liver, or adrenal glands.

Diagnosis

Lung cancer is diagnosed using a variety of methods. Once a diagnosis is confirmed, it is further refined in terms of stage—a classification that describes how advanced it is.

Methods of Diagnosis

The specific methods used to detect lung cancer as well as the number of methods necessary to solidify a diagnosis depend on factors such as whether a person has a history of smoking and the size and location of the tumor once it's detected.

  • Physical examination: A doctor will listen to the lungs, looking at a person's features and fingernails, feel their lymph nodes, and take a complete medical history and symptom profile.
  • Imaging: Various imaging studies may be used to help a doctor visualize a tumor in the lungs: chest X-ray, computerized tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) (which is especially useful for staging cancer and helping to determine best treatment options).
  • Lung biopsy: A biopsy involves removing a sample of tissue from the lung to examine it closely and determine the type of lung cancer. There are several methods for doing this: bronchoscopy endobronchial ultrasound (performed during a bronchoscopy to determine stage of cancer), fine needle biopsy, thoracentesis, mediastinoscopy.
  • Pulmonary function tests (PFTs): These evaluate lung capacity and can help determine the degree to which a tumor is interfering with breathing. Pulmonary function tests include spirometry, diffusion test, and lung plethysmography.
  • Other laboratory tests: Other tests that may be used in the process of lung cancer diagnosis include blood tests, sputum cytology, gene testing, PD-L1 testing, and liquid biopsy. 

Lung Cancer Screening

The U.S. Preventive Services Task Force recommends certain people be screened for lung cancer using computerized tomography once a year. They are those who:

  • Are 50 to 80 years old
  • Have a 20 pack-year or more history of smoking
  • Currently smoke or have quit within the past 15 years
  • Are generally well enough to undergo treatment in the even lung cancer is diagnosed


Staging

Once diagnosed, cancer is staged—that is, labeled based on how advanced it is. To describe the severity of the disease, cancer is staged.

Non-small cell lung cancer is staged based on the American Joint Committee on Cancer (AJCC) TNM system in which TNM stands for Tumor, lymph Nodes, and Metastasis. NSCLC is regarded as stage 4 when it has spread to the second lung, the fluid around the lung or heart, or other distant body areas. 

There are two degrees of stage 4 metastatic NSCLC:

  • Stage 4A: Cancer has spread to the lymph nodes and/or other parts of the body. The spread is within the chest and/or it has spread to one area outside of the chest.
  • Stage 4B: Cancer has spread outside of the chest to more than one place in a single organ or to more than one organ.

Small cell lung cancer can be staged in the same way as NSCLC, but is more commonly classified according to two types of stage:

  • Limited-stage SCLC: Cancer is present on only one side of the chest. Treatment can be with a single radiation field. In most circumstances, the cancer is only in one lung, but it might have reached the lymph nodes on the same side as that lung.
  • Extensive-stage SCLC (metastatic lung cancer): Cancer has spread widely throughout a single lung or it may have spread to the second lung, the lymph nodes, or other parts of the body (including the fluid around the lung).

Treatment

Treating metastatic lung cancer is challenging. At stage 4, the tumor is no longer confined to separate discreet area and the cancer may be affecting organs and systems in the body other than the lungs.

For these reasons, treatment often is focused on palliative care—relieving symptoms, improving quality of life, and extending life rather than attempting to cure the cancer. It takes into account not only physical needs but also psychological, spiritual, and social needs.

NSCLC

All that said, the approach to treating stage 4 non-small cell lung cancer may differ somewhat from that for stage 4 small cell lung cancer. What's more, treatment may ve further refined based on the type of each.

Stage 4A NSCLC: Treatment options may include surgery, chemotherapy, radiation, or a combination of all three. In this stage, cancer is limited to the lungs and one other external location. It is possible that both areas might be treated with surgery and radiation.

Stage 4B NSCLC: Gene mutation testing will often be performed before treatment. If specific gene mutations are identified, then targeted drug therapy will often be the first treatment line.

Also, tumor cells may be tested for the PD-L1 protein. If higher levels of this protein are found, then the cancer is more likely to respond to specific immunotherapy drugs.

In May 2020, the Food and Drug Administration approved Tabrecta (capmatinib) for adults with aggressive stage 4 NSCLC that has spread to other parts of the body. It can be prescribed as a first-line treatment and also for previously-treated patients.

SCLC

Chemotherapy and immunotherapy are used in the first-line treatment of extensive-stage SCLC. Cancer has spread too far for surgery or radiation therapy to be successful as an initial treatment. The combination of chemotherapy and immunotherapy is designed to shrink cancer, alleviate symptoms, and help you live longer.

If cancer responds to this first-line of treatment, then radiation therapy might also be introduced. The goal of radiation is to help prolong life; prophylactic radiation might be considered to prevent cancer progression in the brain.

One of the key differences between NSCLC and SCLC is that SCLC is less responsive to many targeted drugs and immunotherapies. Research has identified that although new therapeutic treatments have emerged, they have not significantly improved patient survival.

Immunotherapy is thought to be the most promising SCLC treatment that has emerged in recent years when combined with chemotherapy or radiation therapy.

Prognosis

The prognosis for metastatic lung cancer typically is measured in terms of survival rates. The Surveillance, Epidemiology, and End Results (SEER) Program of the National Cancer Institute collects and publishes detailed information about cancer incidence and survival in the United States.

The SEER database tracks five-year relative survival rates for NSCLC and SCLC. The five-year survival rate is the percentage of people who will be alive five years after diagnosis. 

The SEER program categorizes data and survival estimates into three stages of lung and bronchus cancer:

  • Localized: Confined to the primary site
  • Regional: Spread to regional lymph nodes
  • Distant: Cancer has metastasized
5-Year Relative Survival by Stage at Diagnosis of Lung and Bronchus Cancer in the United States
  Stage % Cases by Stage    Relative 5-Year Survival Rate
Localized  17% 59%
Regional   22% 31.7%
Distant  57% 5.8%
Note, a proportion of cases are un-staged and the survival rate is unknown, therefore these have not been included in the chart

Survival Estimates

Survival estimates have limitations. They reflect the entire population of people with lung cancer, regardless of age, health, cancer grade, or cancer type. Cancer survival estimates can give a general idea about the survival rate of most people in your situation. However, they can't give your chances of cure or remission as an individual.

Coping

Metastatic lung cancer is not the same thing as "terminal cancer," as it can be treated. During treatment, your doctor, medical team, family, and friends can help you cope with metastatic lung cancer lifestyle changes, symptoms, and treatment side effects. Reach out to them for help and emotional support and also consider these measures:

  • Learn about the disease, metastasis, staging, and treatments. Some people find that increasing their knowledge in these areas helps them to face the disease and treatments. If you want to know more, your doctor will help answer any questions you have. Ask as many questions as you need to feel comfortable with the level of information you want to know. 
  • Talk with a healthcare professional about your worries, emotions, and situation. There is a lot of support available to help you psychologically as well as physically. Your healthcare team is very specialist and experienced. They will be able to help you with coping strategies, psychological support, and lifestyle changes.
  • Take time out. It might seem as if you're always in the doctor's office, hospital, having treatment, or taking medication. It can feel overwhelming. Therefore it's crucial to schedule in time to do something that helps you relax. Whether it is reading, visiting friends, meditation, or watching a movie, make sure you take time out to unwind. 
  • Find a support network. Sometimes it helps to speak to other people who have been through the same cancer stage as you or who are also living with it. Ask your doctor about local support groups that you could attend. Alternatively, there may be an online support group or social media platform where you can find people in a similar situation to speak to.
  • Focus on things you enjoy. It can be tiring going through treatment for metastatic lung cancer. Therefore, focus your energy on doing something you enjoy. Plan your activities for times of the day where you have the most energy. Or plan ahead to make sure you don't have too much on at the same time as something you really want to do. 
  • If you are worried about how your family is coping, encourage them to seek help too. There are in-person and online support groups for family members and carers. 

A Word From Verywell

Although a diagnosis of metastatic lung cancer is at the very least overwhelming, advances in treatment have increased life expectancy over several decades. Survival rates are improving year by year, and death rates from lung and bronchus cancers have been falling on average 3.6% each year since 2009.

Treatments for metastatic lung cancer continue to advance, and there are many ongoing clinical trials. If you have been diagnosed with metastatic lung cancer and want to know how to be considered for a clinical trial, speak with your medical team about your options.

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