Where Does Lung Cancer Spread?

Many people with lung cancer are all too aware that lung cancer can spread. Nearly 40% of those people newly diagnosed with lung cancer already have metastases to other parts of the body. How and where does lung cancer metastasize, and how can you know if your cancer has spread?

Lung cancers can spread when cells break off from the tumor, and travel through the bloodstream or the lymphatics (vessels in the body through which lymph and white blood cells travel) to distant regions of the body and grow. This process is called metastasis.

It is important to distinguish between primary (where a cancer starts) and secondary cancers when talking about the spread or metastasis of cancer. A primary lung cancer that spreads to bone is referred to as “lung cancer metastatic to bone,” not “bone cancer.” Similarly, a lung cancer that spreads to the brain is termed “lung cancer metastatic to the brain” rather than “brain cancer.”

Lung cancer can spread to nearly any region of the body.

Let's take a look at each of these areas separately.

Most lung cancers first spread to lymph nodes in the chest near the tumor. As cancer progresses, cancer cells can travel to areas in the chest further from the initial tumor, and then on to other regions of the body. Unlike metastases to other regions of the body, spread of lung cancer to the lymph nodes doesn’t mean that it is metastatic (stage 4 non-small cell or extensive stage small cell lung cancer).

All lung cancer stages other than stage 1 non-small cell lung cancer can include cancers that have spread to lymph nodes.

Most of the time, the spread of lung cancer to the lymph nodes doesn’t cause any symptoms. When these cancers extend to lymph nodes beyond the lungs, you may notice a lump in your neck or your armpit, similar (but usually firmer) to the swollen glands you may have had in the past with a sore throat.

Treatment is usually chemotherapy unless the lymph nodes that are involved are near the initial tumor and can be removed with surgery.

Roughly 30% to 40% of people with advanced lung cancer have spread (metastases) to bones. The most common bones to be affected are the spine (especially the vertebrae in the chest and lower abdominal area), the pelvis, and the upper bones of the arms and legs (humerus and femur). Lung cancer is also somewhat unique in that it can spread to the hands and feet.

The most common symptom of bone metastases is pain. Often the pain begins gradually, feeling like a muscle pull or strain, and progresses to more severe pain. Due to weakening of the bone from the tumor, some people develop fractures (pathological fractures) that occur with minimal trauma or even during normal daily activities.

If lung cancer spreads to the spine, it may put pressure on the spinal cord (spinal cord compression) which can be a medical emergency. This may cause weakness or tingling in your legs or difficulty walking. Cancers that metastasize to bone may also break down bone releasing calcium into the blood (hypercalcemia) causing symptoms of confusion, muscle weakness, and loss of appetite among others.

Tests to look for bone metastases may include a bone scan, PET scan, CT, or MRI. The primary goal in treatment of bone metastases is to reduce pain and to repair or prevent fractures that occur. Options include pain medications, radiation therapy, medications to try to prevent the breakdown of bone, and surgery to stabilize bones.

Lung cancer is the most common cancer that spreads to the brain, and as many as 40% of people with advanced lung cancer will develop brain metastases some time during their disease. Both non-small cell lung cancer and small cell lung cancer can spread to the brain. Small cell lung cancer can spread to the brain rapidly, often before a diagnosis is even made. Prophylactic cranial irradiation (PCI), a type of radiation therapy, may be used to attempt to prevent this from occurring.

Lung cancer that has spread to the brain can cause symptoms both by destroying brain tissue and by creating inflammation and swelling that places pressure on structures in the brain. In about 44% of people, no symptoms are present.

Common symptoms can include headaches, seizures, loss of balance and coordination, difficulty with speaking, vision changes, loss of memory and personality changes, weakness on one side of the body, and fatigue.

Lung cancer metastatic to the brain is usually diagnosed with either a CT scan or an MRI of the brain.

Treatment is primarily palliative, meaning that the goal is to control symptoms and not to try to cure the cancer. Steroids may be used to decrease swelling. Pain medications and anti-seizure medications may be used to control headaches and seizures. Radiation therapy may be very effective in reducing symptoms for some people.

If only one or a few brain metastases are present - something referred to as "oligometastases" - treatment with either surgery or stereotactic body radiotherapy (SBRT) also known as cyber knife or gamma knife, has resulted in long-term control of the disease for some people.

Lung cancer that has spread to the liver may not cause any symptoms and is often discovered when a test, such as a CT scan, is done to look for spread of your cancer. When symptoms are present, they may include pain under your ribs on the right side of your body, loss of appetite, and nausea. If there are many tumors in your liver or if the metastases are large enough to obstruct ducts in your liver, you may develop jaundice (a yellow coloring of your skin and the whites of your eyes).

Tests that are done to look for spread of lung cancer to the liver may include an abdominal ultrasound, a CT scan of your abdomen, or a PET scan.

Treatment is usually chemotherapy designed to treat the primary cancer as well. In rare cases, if only a single tumor or a few tumors are present, surgery may be recommended to remove the tumors. Sometimes a procedure called embolization may be recommended as well. This is a procedure that stops the blood flow to part of the liver so cancer cells that are present can’t survive.

Lung cancer spread to the adrenal glands (small glands that sit on top of the kidneys and produce hormones), does not usually cause any symptoms, and is most often discovered incidentally when a scan is done to stage cancer.

Treatment with chemotherapy for the cancer may be helpful. In a very small number of people who were able to have their lung cancer removed and had only one spot in one of the adrenal glands, surgery to remove the adrenal gland and adrenal metastases has resulted in long-term survival.

While the regions above are the most common sites for lung cancer metastases, lung cancer has on occasion spread to the stomach, small and large intestines, the pancreas, the eye, the skin, the kidney, and even the breast.

Other than spread to lymph nodes which can include earlier stages of the disease, lung cancer that has spread to distant regions of the body is classified as stage 4 non-small cell lung cancer or extensive stage small cell lung cancer. The overall 5-year survival rate for stage 4 non-small cell lung cancer is sadly only around 1%. The median survival, that is the amount of time after which half of people are still alive and the other half have passed away, is 8 months. The overall 5-year survival rate for extensive stage small cell lung cancer is 2%. Average survival is 6 to 12 months with treatment, but only 2 to 4 months without treatment.

That said, there are people who have survived and done well for many years even after a diagnosis of lung cancer that has spread. 

As noted above, under the heading for particular areas of the body to which lung cancer may spread, is that when only a few sites of metastasis are present, treating these metastases with a goal of long-term control of the cancer rather than just palliation may be considered. Many researchers now believe that advances in treatment approaches for people with only a few metastases has made it possible for some people with oligometastases due to lung cancer to have long term disease free survival with an excellent quality of life.