Metastatic cancers are associated with the primary (or original) cancer. For example, lung cancerthat spreads to the liver is called metastatic lung cancer, rather than liver cancer.
Metastatic tumors are very common in later stages of lung cancer, typically called stage 4 lung cancer, or advanced lung cancer.
Metastatic vs. second primary cancer
Metastatic cancers are associated with the primary cancer, rather than the site of metastasis. This is because when they are examined under a microscope, the cancer cells are shown to retain the features of the primary cancer.
This is also how doctors are able to distinguish between a metastatic cancer and a second primary cancer.
Second primary cancers are not metastases, but new cancers that are unrelated to the first type of cancer.
Second primary cancers are rare. Usually when someone with cancer is told they have cancer again, it means that the first primary cancer has returned. In lung cancer patients, for example, this means that the cancer has returned to the same part of the same lung after treatment. This is called recurrent lung cancer.
If cancer develops in the lung that was previously unaffected, it is usually considered to be a metastatic tumor rather a primary cancer that has returned.
Where does lung cancer spread to?
If lung cancer spreads, it typically spreads to certain areas such as:
- adrenal glands
- bones
- brain
- liver
- lymph nodes
In rare cases, it may spread to other areas of the body including the stomach, intestines, pancreas, and kidney.
Lung cancer occurs when healthy cells mutate during the cell division process to become cancer cells. These cancer cells continue to multiply until they eventually form a tumor on the lung.
As the tumor grows, it requires more space in the body and so begins to spread to other parts of the body. This spread is the start of metastatic lung cancer.
The cancer cells spread by growing directly into nearby tissue, or by breaking away from the primary tumor and traveling through the bloodstream or lymphatic system.
Growing directly into nearby tissue
The tumor pushes on the healthy tissue nearby, forcing itself to break through. As it continues to grow, the cancer blocks small blood vessels in the area.
This leads to a reduction in the supply of blood and oxygen to the healthy tissue. Without blood and oxygen, the normal tissue begins to die off, allowing the cancer to spread further.
Traveling through the bloodstream or lymphatic system
In order to spread via blood or lymph, cells from the tumor must break away.
Healthy cells contain substances called adhesion molecules that allow them to stick together. Research suggests that cancer cells no longer adhere to normal tissue structures.
In addition, scientists have discovered cancer cells secrete substances called exosomes, which may stimulate them to move. Research is ongoing into the role these exosomes play in the spread of cancers.
Cancer cells that travel through the bloodstream can eventually get stuck in a small blood vessel. Those that survive move through the wall of this blood vessel into nearby tissue. Here they may grow and form a new tumor.
Cells that travel through the lymph vessels can also get stuck. If the cells are not destroyed by the lymph glands, they form tumors in the lymph nodes.
Symptoms
The symptoms of metastatic lung cancer are related to the area to which it spreads. However, the associated symptoms can be quite general and may be related to other issues. It is important to note that metastatic cancer does not always cause symptoms.
Some common symptoms related to the site of the metastatic lung cancer are:
- Adrenal glands: Cancer that spreads to the adrenals does not usually cause symptoms. However, the level of adrenal hormones may drop, leading to weakness and tiredness.
- Bones: Up to 40 percent of patients with advanced lung cancer develop bone metastases. Pain is the main symptom. The risk of fractures also increases.
- Brain: Between 20 and 40 percent of patients with non-small-cell lung cancer, which is a type of lung cancer accounting for 85 percent of lung cancers, develop brain metastases. Headaches, confusion, tiredness, nausea, and weakness are symptoms.
- Liver: Loss of appetite, nausea after eating, or pain under the right ribs can indicate cancer in the liver. Jaundice, a yellowing of the skin and whites of the eyes, is another symptom.
- Lymph nodes: Enlarged lymph nodes, which are located in the armpit, neck, and stomach, can suggest the cancer has spread. Although, these nodes also swell during other types of illness.
Diagnosis
Testing for metastases involves checking areas where lung cancer typically spreads to. Other areas may be investigated for metastases dependent on symptoms and results of initial tests.
Diagnostic tests include:
- blood tests
- bone scans
- X-rays
- CT scans
- MRI scans
- ultrasounds
Prevention
Simply having cancer or a history of cancer is a risk factor for metastases, and doctors cannot predict who will develop metastatic cancer. So, preventing metastatic lung cancer means preventing or promptly treating primary lung cancer.
Certain risk factors that predispose people to lung cancer, such as genetics, are unavoidable. However, other factors can be avoided.
Quitting smoking is the most important preventive measure that can be taken to reduce the risk of developing primary lung cancer.
Avoiding secondhand tobacco smoke and contact with certain materials, such as asbestos and radon, also reduces risk.
Screening for lung cancer
Screening techniques are available to people who are at an increased risk of lung cancer. Early detection means a treatment program can be put in place before the cancer progresses, or spreads to other areas of the body.
People who are 55 or older, have a family history of lung cancer, smoke, or are former smokers may wish to discuss lung cancer screening options with their doctor.
Treatment
Metastatic lung cancer treatment focuses on controlling cancer growth and relieving symptoms. Treatment options used depend on the type of lung cancer, the location of the metastases, treatments carried out in the past, and general health.
Options include:
- Chemotherapy or biological therapy: This is usually offered if the cancer has spread to more than one area of the body.
- Radiotherapy: May be used if the cancer has spread to just one area.
- Laser therapy: Used to burn away part of a tumor, which may be blocking an airway.
- Other medications: These are offered to address specific symptoms. Examples include steroids, muscle relaxants, and pain killers.
Outlook
Not all lung cancers spread. However, once cancer has spread to other organs, the National Cancer Institute advise that it is not curable. At this stage, people are treated in order to control their symptoms and try to prolong their life.
According to the American Cancer Society, 26 percent of people diagnosed with a late-stage lung cancer that has metastasized to other areas of the body, live for at least one year after diagnosis. The 5-year survival rate is 4 percent.
Coping
People who are told that their metastatic lung cancer cannot be controlled are advised to discuss end-of-life care with both a doctor and loved ones.
Intense emotions such as anger, anxiety, confusion, and grief are common reactions for people with cancer. It can be helpful to:
- seek support from friends and family
- join a cancer support group
- attend counseling
- talk to a doctor or nurse regarding any queries on diagnosis or treatment
When to see a doctor
If someone has been diagnosed with primary lung cancer, they should make sure to attend all scheduled appointments and treatments with their doctor or other healthcare provider.
If new symptoms develop and persist for more than a few days, it is important to discuss these with a doctor.