Lung cancer develops in one area of the body and may then spread to other areas. The spread of cancer is called metastasis.
This type of metastatic cancer is common in the advanced stages of lung cancer. It can be challenging to treat and often has a poor prognosis.
In this article, we look at how lung cancer spreads to different organs, its effects on the body, and how doctors treat it.
If lung cancer spreads, it typically invades specific areas, such as:
- adrenal glands
- lymph nodes
In rare cases, it may spread to other areas of the body, including:
Metastatic cancers take the name of the primary cancer rather than the organ or area to which it has metastasized.
People can also develop a second primary cancer. These forms of cancer are not metastases. Instead, they are new primary cancers in someone who has had cancer in the past.
Closer tissue examination using a microscope allows a doctor to distinguish between metastatic cancer and a second primary cancer.
In metastatic lung cancer, the cells keep the features of the original cancer.
Second primary cancers are rare and usually occur months or years after diagnosis and treatment of the original, or primary, cancer.
Typically, a diagnosis of metastatic cancer means that the first primary cancer has returned.
In people with lung cancer, for example, this means that the disease has returned to the same part of the original lung after treatment. Doctors call this recurrent lung cancer.
If cancer develops in the opposite lung, a doctor will usually consider this to be a metastatic tumor, rather than primary cancer.
Lung cancer develops when normal cells mutate as they divide, becoming cancerous. These cancer cells continue to multiply without dying until they eventually form a lung tumor.
When a tumor grows and becomes more aggressive, it requires more space and begins to spread to other areas. This stage is the start of metastatic lung cancer.
The cancer cells spread in two ways. They may directly enter nearby tissue. Alternatively, the cells might break away from the primary tumor and travel through the bloodstream or lymphatic system.
Growing directly into nearby tissue
When a tumor pushes on noncancerous tissues nearby, it can force its way through. As its growth continues, cancer blocks small blood vessels in the area.
This blockage reduces the blood and oxygen supply to the healthy tissue. Without consistent blood and oxygen, the tissue begins to die, allowing cancer to spread further.
Traveling through the bloodstream or lymphatic system
Cells can break away from a primary tumor to spread through the blood or lymph nodes.
Healthy cells contain substances called adhesion molecules that allow them to stick together.
A 2019 study in the Journal of Cancer suggests that the loss of function in adhesion molecules may contribute to metastasis.
Scientists have also discovered that cancer cells secrete substances they call exosomes that stimulate the cells to move. Research is ongoing into the role these exosomes play in metastasis.
Cancer cells that travel through the bloodstream can eventually stick in a small blood vessel. Those that survive move through the wall of this blood vessel into nearby tissues. They may then grow and form a tumor at this new site.
Cells that travel through the lymph vessels can also become stuck. The lymph nodes play an active role in the body's immune defense system. If these lymph glands do not destroy the cells, the metastasized cancer may form tumors in the lymph nodes.
Metastatic cancer does not always cause symptoms.
If symptoms of metastatic lung cancer do appear, they will depend on where cancer has invaded. They may be quite general and may seem to relate to other health issues.
Some common symptoms of metastatic lung cancer at different sites include:
- Adrenal glands: Cancer that spreads to the adrenal glands does not usually cause symptoms. However, it may lead to reduced levels of adrenal hormones. This may trigger feelings of weakness and fatigue.
- Bones: Around 30–40% of people with advanced lung cancer develop bone metastases when pain is the main symptom. The risk of fractures also increases.
- Brain: Between 20–35% of individuals with non-small cell lung cancer develop brain metastases. Headaches, confusion, tiredness, nausea, and weakness are symptoms.
- Liver: Appetite loss, nausea after eating, or pain under the right ribs can indicate liver cancer. Jaundice is another symptom when yellowing of the skin and whites of the eyes occurs.
- Lymph nodes: Enlarged lymph nodes in the armpit, neck, and stomach can suggest that lung cancer has spread. However, these nodes also swell during other illnesses.
Testing for metastases involves checking the areas and organs where lung cancer typically spreads. A doctor may investigate other areas for metastases, depending on symptoms and results of initial tests.
Diagnostic tests include:
Doctors cannot predict who will develop metastatic cancer.
Having lung cancer or a history of lung cancer is a risk factor for metastases. Hence, preventing metastatic lung cancer means avoiding the risk factors of primary lung cancer.
Early detection and treatment are also vital for preventing the spread of lung cancer.
Certain risk factors, such as genetics or family history, are unavoidable. However, it is possible to reduce other risk factors.
Smoking cessation is the most critical, preventive measure for reducing the risk of primary lung cancer.
Avoiding secondhand tobacco smoke and contact with certain harmful materials, such as asbestos and radon, also reduces the risk.
Screening for lung cancer
Screening is available to people who have a high risk of lung cancer. Early detection means that a doctor can develop an effective treatment before the cancer metastasizes.
Those who may wish to discuss screening options with their doctor include:
- people over 55 years of age
- someone with a family history of lung cancer
- individuals who currently smoke
- people who used to smoke within the last 15 years
Metastatic lung cancer treatment focuses on controlling cancer growth and relieving symptoms. If the cancer has spread, it can be difficult to eliminate it from the body completely.
Treatment options depend on the type of lung cancer, the location of the metastases, treatments carried out in the past, and a person's general health.
- Chemotherapy or biological therapy: This is usually appropriate if the cancer has spread to more than one area of the body.
- Radiation therapy: A doctor might request this if cancer has spread to just one area.
- Laser therapy: The cancer care team may use lasers to burn away part of a tumor, which may be blocking an airway.
- Other medications: These address specific symptoms as they arise. Examples include steroids, muscle relaxants, and painkillers.
Not all lung cancers spread. However, most types of metastatic cancers cannot be cured, according to the National Cancer Institute. Most people receive treatment to control their symptoms and improve their quality of life.
According to the American Lung Association, people with lung cancer that has spread to distant organs have a 5-year survival rate of 5%.
This figure means that a person with a diagnosis of metastatic lung cancer is only 5% as likely as an individual without cancer to survive for 5 years beyond the date of diagnosis.
Coping with metastatic lung cancer
People who have a diagnosis of metastatic lung cancer may need to discuss end-of-life care with both a doctor and their loved ones.
This process can lead to intense emotions, such as anger, anxiety, confusion, and grief. The following steps can help a person manage the emotional impact of metastatic lung cancer:
- seeking support from friends and family
- joining a cancer support group
- attending counseling
- talking to a doctor or nurse about a diagnosis or treatment
When to see a doctor
If a person receives a diagnosis of primary lung cancer, they should attend all scheduled appointments and procedures with their doctor or other healthcare professionals.
If new symptoms develop and persist for more than a few days, it is essentials to discuss these with a doctor as soon as possible.
Does lung cancer spread more quickly than other cancers?
How quickly cancers spread depends on a multitude of factors such as an individual’s health status, type of lung cancer, and response to treatment. For example, a type called large cell (undifferentiated) carcinoma, which accounts for about 10–15% of lung cancers, tends to grow and spread quickly, which makes it harder to treat.
Comparing the likelihood of lung cancer spreading quicker than other cancers requires more specialized studies.Christina Chun, MPH Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.