Metastatic Cancer: When Cancer Spreads

This page is for people told their cancer has spread, and the people who care for them. It explains what metastatic cancer is, where it tends to go, and what treatment can do.

Cancer that spreads from where it started to a distant part of the body is called metastatic cancer. For many types of cancer, it is also called stage 4 cancer. The process by which cancer cells spread to other parts of the body is called metastasis.

Doctors look at metastatic cancer cells under a microscope and test them in other ways. The cells have features like the primary (original) cancer. They do not look like the cells in the place where the metastatic cancer was found. That is how doctors can tell the cancer has spread from another part of the body.

Metastatic cancer keeps the name of the cancer it came from, no matter where it travels.

Metastatic cancer has the same name as the primary cancer. Take breast cancer that spreads to the lung. It is called metastatic breast cancer, not lung cancer. And it is treated as stage 4 breast cancer, not as lung cancer.

Sometimes doctors cannot tell where a metastatic cancer started. That type is called cancer of unknown primary origin, or CUP.

Cancer cells spread through the body in a series of steps. These steps include:

1. growing into, or invading, nearby normal tissue.
2. moving through the walls of nearby lymph nodes or blood vessels.
3. traveling through the lymphatic system and bloodstream to other parts of the body.
4. stopping in small blood vessels at a distant site, invading the vessel walls, and moving into the tissue around them.
5. growing in this tissue until a tiny tumor forms.
6. causing new blood vessels to grow. That creates a blood supply, which lets the metastatic tumor keep growing.

Most of the time, spreading cancer cells die at some point along the way. But if conditions stay right for the cancer cells at every step, some of them can form new tumors elsewhere in the body. Metastatic cancer cells can also lie inactive at a distant site for many years before they start growing again, if at all.

Cancer can spread to almost any part of the body. But different types of cancer tend to spread to certain areas more than others. The most common sites where cancer spreads are bone, liver, and lung.

Here are the main sites where common cancers spread, not counting the lymph nodes. The peritoneum is the thin lining of the belly.

• Bladder: bone, liver, lung.
• Breast: bone, brain, liver, lung.
• Colon: liver, lung, peritoneum.
• Kidney: adrenal gland, bone, brain, liver, lung.
• Lung: adrenal gland, bone, brain, liver, other lung.
• Melanoma: bone, brain, liver, lung, skin, muscle.
• Ovary: liver, lung, peritoneum.
• Pancreas: liver, lung, peritoneum.
• Prostate: adrenal gland, bone, liver, lung.
• Stomach: liver, lung, peritoneum.

Metastatic cancer does not always cause symptoms. When symptoms do happen, what they feel like and how often they come depend on the size and location of the metastatic tumors. Some common signs include:

• pain and fractures, when cancer has spread to the bone.
• headache, seizures, or dizziness, when cancer has spread to the brain.
• shortness of breath, when cancer has spread to the lung.
• jaundice (yellowing of the skin or eyes) or swelling in the belly, when cancer has spread to the liver.

There are treatments for most types of metastatic cancer. Often the goal is to control the cancer by stopping or slowing its growth. Some people live for years with metastatic cancer that is well controlled.

Other treatments may improve quality of life by easing symptoms. That kind of care is called palliative care. It can be given at any point during cancer treatment.

Which treatment a person has depends on several things:

• the type of primary cancer
• where it has spread
• treatments they have had in the past
• their general health

For cancer-specific next-step guides, see metastatic breast cancer, stage 4 lung cancer, metastatic colorectal cancer, metastatic prostate cancer, and oligometastatic cancer.

If a person is told their cancer can no longer be controlled, they and their loved ones may want to talk about end-of-life care. Palliative care is always available, whether or not someone chooses to keep treating the cancer. It is there to control symptoms of cancer and side effects of treatment.

Researchers keep studying new ways to kill primary and metastatic cancer cells, or to stop them growing. That work includes helping the immune system fight cancer, blocking the steps that let cancer cells spread, and targeting specific genetic changes in tumors.

Even after cancer spreads, there are treatment options, and care to help people feel better is always available.