Where Does Lung Cancer Spread?

One of the biggest concerns among people with lung cancer is that the cancer may spread to other parts of the body. This is known as metastasis (plural metastases) and occurs in around 40% of newly diagnosed people. Although this can occur in any part of the body, there are several sites where it is more common.

The article details the five sites where lung cancer most commonly spreads as well as the symptoms it can cause in each location. It also details what can be done to treat it and offers insights into the prognosis (likely outcome) of metastatic lung cancer.

How Does Lung Cancer Spread?

Lung cancer spreads when cancer cells break off from the primary (original) tumor and travel through the bloodstream or lymphatic system. The lymphatic system is a network of vessels and organs that collects, carries, and filters substances from the body, including cancer cells.

Where Does Lung Cancer Spread?

The most common areas for lung cancer to spread are:

• Lymph nodes
  
• Bones
• Brain
• Liver
• Adrenal glands

Less commonly, lung cancer can spread to the stomach, intestines, pancreas, eyes, skin, kidneys, or breast.

Different stages of the disease indicate how much the cancer has grown and spread. Local spread is known as stage 2. Metastasis occurs when cancer spreads to distant sites. Unlike early-stage cancer that may be cured, metastatic cancer (also known as stage 4 cancer) cannot and is instead managed.

The risk of metastatic lung cancer can also vary by the cancer type. This includes the more common non-small cell lung cancer (NSCLC) and the less common small cell lung cancer (SCLC).

Lymph Nodes

Most lung cancers first spread to lymph nodes within the lung or around the major airways. Lymph nodes are tiny organs clustered throughout the body that trap and filter foreign substances.

As long as cancer only spreads to nearby lymph nodes, it isn't considered metastatic. The local spread of cancer to the lymph nodes can occur during stage 2 NSCLC or limited-stage SCLC. People at this stage often have no symptoms.

If left untreated, the cancer can spread to distant lymph nodes and other sites in the body. It is at this stage (called stage 4 NSCLC or extensive-stage SCLC) that you may notice a hardened lump in the neck or armpit where a lymph node has cancer cells.

Surgery is the first-line treatment for early-stage NSCLC and includes the partial or complete removal of nearby lymph nodes. Other treatments such as radiation, chemotherapy, and targeted therapy may be used with surgery or on their own for people with metastatic disease.

Bone

One of the more serious complications of NSCLC is lung cancer metastases to bones. Roughly 30% to 40% of people with advanced lung cancer will develop this.

The areas most affected by bone metastases include:

• Spine
• Pelvis
• Thigh bone
• Upper arm bone
• Hands and feet

Pain is the most common symptom. The pain often starts gradually, feeling more like a muscle pull or strain, before turning severe. More severe symptoms may include:

• Pathologic fractures, which is when the bone breaks in an area weakened by disease
• Hypercalcemia (high calcium levels in the blood), a condition that can cause symptoms such as confusion, muscle weakness, and loss of appetite
• Spinal cord compression, if the cancer spreads to the spine

The primary goal of treatment is to reduce pain and prevent fractures. Options include pain medications, radiation, surgery, and drugs used to slow the breakdown of bone.

Brain

Lung cancer is the most common cancer that spreads to the brain. In fact, as many as 40% of people with lung cancer will develop brain metastases at some point. This can occur with both NSCLC and SCLC but is known to develop rapidly with SCLC.

As many as 44% of people will have no symptoms at all when lung cancer has spread to the brain. Others may experience:

• Headache, often with nausea or vomiting
• Confusion
• Memory loss
• Seizures
• Vision loss
• Numbness or weakness on one side of the body

The treatment is primarily palliative, meaning that the goal is to control symptoms rather than cure the disease. This may involve pain medications, anti-seizure drugs, radiation to shrink tumors, or steroids to decrease brain swelling.

If there are few metastases, surgery or a form of radiation called stereotactic body radiotherapy (SBRT) may be used. For people at risk of brain metastases, another type of radiation called prophylactic cranial irradiation (PCI) may be used to prevent this from occurring.

Liver

Lung cancer that has spread to the liver is common and can affect anywhere from 30% to 50% of people with advanced-stage disease.

Many people with liver metastases will have no symptoms, but those who do may experience:

• Loss of appetite
• Weight loss
• Fatigue
• Leg swelling
• Itching
• Jaundice (yellowing of the skin or eyes)

Chemotherapy is usually recommended to treat both the primary tumor and cancer cells in the liver. This sometimes involves transarterial chemoembolization, a procedure in which a tube called a catheter delivers chemotherapy drugs directly to the liver.

In rare cases, if only a single tumor or a few tumors are found, they may be removed with surgery.

Adrenal Glands

Adrenal glands are organs on the top of the kidneys that produce hormones. Lung cancer that spreads to the adrenal glands does not usually cause symptoms and is most often discovered during the routine staging of cancer.

Treatment with chemotherapy is useful in extending survival. In cases where the lung tumor can be resected (removed), the affected adrenal gland may be removed as well.

How Quickly Does Lung Cancer Spread?

Every cancer is different, so there isn't one answer to this question.

One way to determine how fast any cancer might spread is by examining how long it takes to double in size. The thinking is that the faster it grows, the quicker it may spread. Researchers have found that it takes approximately three to six months for a lung cancer tumor to double in size.

The type of cancer also plays a role in how quickly lung cancer can spread. For example, small cell lung cancer can spread very early regardless of its size, while squamous cell carcinomas of the lung spread when they are larger.

The speed at which lung cancer spreads also depends on whether a tumor has specific mutations that help them spread.

How Is Metastatic Lung Cancer Treated?

Treatment will depend on the patient's individual circumstances, such as age, overall health, and where in the body the cancer has spread. The goal of treatment is to slow or stop the tumor's growth and alleviate symptoms.

Treatment plans typically involve a combination of the following:

• Immunotherapies to help the body fight off cancer
• Targeted drug therapy to target abnormalities in tumors
• Chemotherapy to slow the growth of cancer cells

At this stage, surgery may not be an option if the cancer is too widespread. Patients will typically receive palliative care.

Can Metastatic Lung Cancer Be Cured?

In most cases, metastatic lung cancer is not curable. Some research has shown that certain people with a single metastasis can be cured with surgery, but the cure rate is low and more research is needed.

Other than the spread of cancer to nearby lymph nodes, lung cancer that has metastasized generally has poor outcomes. According to the National Cancer Institute (NCI), the overall five-year survival rate for metastatic lung cancer is 6.3%. This means that around six of every 100 people diagnosed with metastatic lung cancer will live five years or more.

This doesn't mean your chances of survival are necessarily low, however. NCI statistics are based on all people with stage 4 lung cancer, some of whom may be older, less healthy, or have different types of cancer than you. Other issues factor into your individual odds of survival, not least of which is your performance status (a measurement of your ability to perform everyday tasks).

There are also drugs called checkpoint inhibitors, which include Keytruda (pembrolizumab) and Opdivo (nivolumab), that have greatly improved survival times in people with metastatic lung cancer.

Summary

The five parts of the body where lung cancer commonly spreads are the lymph nodes, bones, brain, liver, and adrenal glands. The spread may be limited to nearby lymph nodes, where the cancer is more readily treated. If it spreads to distant organs, it is referred to as metastatic lung cancer and is considered incurable.

Even so, there are drugs and treatments that can manage metastatic lung cancer and control symptoms. Although the prognosis of stage 4 lung cancer is generally poor, some people live for many years due to advances in treatment.