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, including non-small cell lung carcinoma (NSCLC) and small cell lung carcinoma (SCLC).

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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How Lung Metastasis Occur

Cancer tumor cells usually form in one primary site of the body. However, cancer cells can break away from the primary site and travel to other body parts in some cases.

When these cells form in distant parts of the body, away from the primary site, they are known as metastasis. Metastasis is usually an indicator that the primary tumor is particularly aggressive.

There are several ways in which cancer cells can spread. The process usually begins with cancer cells invading tissues close to the primary site. They can then move into lymph nodes and blood vessels nearby.

Once in these areas, the cancer cells can travel through the bloodstream or lymphatic system to distant parts of the body. At any point, the cancer cells might leave the vessels or lymphatic system and invade tissues nearby. Once settled, they continue to grow until another tumor (metastasis) forms. 

When cancer spreads, it retains the same name as the original cancer. For example, 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.

Symptoms

Lung cancer can be challenging to diagnose. Early symptoms like coughing or feeling tired are often not severe enough to see a healthcare provider. Because of this, many people are not diagnosed until the disease is advanced.

The most common lung cancer symptoms include; a persistent cough, shortness of breath on exertion, multiple chest infections, coughing up blood, unexplained weight loss, or pain in the chest, back, arm, or shoulder areas. 

In metastatic lung cancer, additional symptoms can develop as the metastases start to grow and affect the function of the organs they invade. Signs and symptoms metastases may present as follows:

  • Brain metastases: Dizziness, visual changes, balance problems, headaches, or seizures 
  • Bone metastases: Pain, fractures, or spinal cord compression
  • Liver metastases: Jaundice (yellowing of the skin) or a swollen abdomen 
  • Adrenal gland metastases: Weight loss, abdominal pain, nausea, vomiting, back pain, weakness, fatigue, fever, or confusion 

Staging

There are different types of lung cancer, and they all can metastasize, some faster than others. The two most common types of lung cancer are NSCLC, which accounts for 80-85% of cases, and SCLC, which accounts for roughly 15% of cases.

To describe the severity of the disease, cancer is staged. This helps to guide the treatment plan. Staging can be complicated, so do not be afraid to ask your doctor what the staging means if it does not make sense.

NSCLC is usually staged using the American Joint Committee on Cancer (AJCC) TNM system. The initials TNM stand for Tumor, lymph Nodes, and Metastasis.

Staging NSCLC

A very brief overview of the stages of NSCLC is as follows:

  • Stage 0: Also known as precancer, or carcinoma in situ. Doctors may have identified cancer cells through a computed-tomography scan or other lung cancer screening tests. It is limited to the linings of the airways. It isn't thought to have spread to the deeper lung tissues, lymph nodes, or other body parts. 
  • Stage 1 NSCLC: The tumor is invasive but cancer has not spread to nearby lymph nodes or distant body parts. It is sub-staged depending on size.
  • Stage 1a: It is no larger than 3 centimeters (cm) across. The invasive part in the deeper lung tissues is no more than ½ cm across. 
  • Stage 1b: It is larger than 3 cm across but not larger than 4 cm. The tumor has grown into either a main airway or the lung membranes.
  • Stage 2 NSCLC: Describes localized lung cancer that is either contained in one lung or has spread to the lymph nodes on that side of the lung. The tumor may have spread to nearby lymph nodes, airways, or visceral pleural tissues.
  • Stage 3 NSCLC: Cancer has spread to nearby tissues or organs such as the carina lymph nodes, hilar lymph nodes, heart, diaphragm, the supraclavicular lymph nodes, or the other side of the chest. Stage 3 is broken into further sub-stages based on the tumor's size and which lymph nodes the cancer has spread to. It has not spread to distant parts of the body.
  • Stage 4 NSCLC (metastatic lung cancer): This is the most advanced stage of lung cancer. Cancer may have spread to the second lung, the fluid around the lung or heart, or other distant body areas. 
  • 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: In this case, cancer has spread outside of the chest to more than one place in a single organ or to more than one organ.

Staging SCLC

SCLC can be staged in the same way as NSCLC, but it is more commonly classified with two stages:

  • Limited-stage SCLC: In this stage, cancer is only present on 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): This SCLC stage might be when cancer has spread widely throughout one single lung. Alternatively, it may have spread to the second lung, the lymph nodes, or other parts of the body (including the fluid around the lung).

Less common types of lung cancer include carcinoid tumors and mesothelioma, which are both staged similarly to NSCLC. 

Diagnosis

Diagnosing lung cancer can be difficult due to symptoms not always being present or severe enough to visit a doctor. In the United States, 57% of all lung cancers are metastatic at the time of diagnosis. To diagnose, stage, and grade lung cancer, several tests and procedures are conducted:

  • Screening: Screening is offered to patients with no lung cancer symptoms but who may be more at risk of developing lung cancer. This includes people between the ages of 55 and 80 with a heavy smoking history, who either continue to smoke or quit within the last 15 years
  • Physical examination: Involves a doctor giving you a full examination, including listening to the lungs, looking at your features and fingernails, feeling your lymph nodes, and taking a complete medical history and symptom profile.
  • Imaging: Various imaging studies can be used to help diagnose lung cancer including, chest X-ray, computerized tomography (CT) scan, magnetic resonance imaging (MRI) scan, and positron emission tomography (PET) scan. 
  • Lung biopsy: A biopsy is when a small sample of tissue is taken from the lung to examine it more closely and determine the type of lung cancer. Clinicians can carry out many different techniques to obtain a lung biopsy. The most common procedures include bronchoscopy, endobronchial ultrasound, fine needle biopsy, thoracentesis, or mediastinoscopy.
  • Pulmonary function tests: These are a range of tests that test lung capacity. They can help identify how much a tumor is interfering with breathing.
  • Other laboratory tests: Other tests that might be performed during the diagnosis of lung cancer include blood tests, sputum cytology, gene testing, PD-L1 testing, and a liquid biopsy. 

Treatment

Treatment for metastatic lung cancer will differ depending on the type of cancer being treated. At stage 4, metastatic cancer has already spread, making it difficult to cure. Treatment options include:

  • Surgery
  • Chemotherapy
  • Targeted therapy
  • Immunotherapy
  • Radiation therapy

In many cases, these treatments will help you live longer, relieve symptoms, and improve your quality of life. However, stage 4 metastatic lung cancer is difficult to cure. 

For some people, the treatments offered may be palliative. Palliative care is a range of care and treatments given to improve people's quality of life who have severe or life-threatening cancer.

Palliative care doesn't just take the disease and physical needs into account. It addresses the person as a whole, including their psychological, spiritual, and social needs. The goal of palliative care is to ease side effects, relieve symptoms, and improve quality of life. 

NSCLC

For stage 4A NSCLC, treatment 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.

For stage 4B NSCLC, gene mutation testing will often occur before any 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.

Chemotherapy is commonly used alongside other treatments for metastatic lung cancers. Your treatment plan will also depend on your overall health. Although treatment at this stage is unlikely to cure metastatic lung cancer, clinical trials of newer treatments might be available.

New Targeted Therapies

In May 2020, the FDA approved Tabrecta (capmatinib), the first targeted drug for stage 4 NSCLC.

This targeted drug is for treating adult patients with aggressive NSCLC that has spread to other parts of the body. It is approved for first-line and 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 you live longer, and 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.

The breakthroughs in targeted therapy treatments for NSCLC have not materialized for SCLC.  However, progress is being made with immunotherapy treatment.

Immunotherapy is thought to be the most promising SCLC treatment that has emerged in recent years when combined with chemotherapy or radiation therapy. Research is ongoing, and scientists believe more treatment breakthroughs are coming for patients with SCLC.

Prognosis

Prognosis is the likely outcome of a situation, such as the likely course of a disease. The type and stage of metastatic lung cancer will influence the prognosis, along with a patient's general health and any other medical conditions they may have.

Doctors will often look at a patient's general health and strength to aid them in making decisions about the right treatment option for that individual. 

The prognosis of metastatic lung cancer is typically 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%
Please 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, irrespective 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

Receiving a diagnosis of metastatic lung cancer can be daunting, especially when it is often metastatic at the point of diagnosis. However, metastatic lung cancer is not the same thing as "terminal cancer." There are many treatment options available.

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. 

Some people find that they following tips help them to cope with living with metastatic lung cancer:

  • 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 like you are 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 can seem 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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