What is metastatic cancer?

Metastatic cancer is cancer that has spread from where it started to another part of the body. The original cancer is called the primary tumour. The cancer in another part of the body is called metastatic cancer. Metastatic cancer has the same type of cancer cells as the primary cancer. For example, when colon cancer spreads to the liver, the cancer cells in the liver are colon cancer cells. It is metastatic colon cancer, not liver cancer.

Metastatic cancer is also called:

• metastatic tumour, tumours or disease
• metastasis (one cancerous tumour)
• metastases (more than one cancerous tumour)
• advanced cancer

All cancers can spread. But the term metastatic cancer is usually only used to describe solid tumours, such as breast, prostate or lung cancer, that have spread to another part of the body. Blood cancers, such as leukemia, lymphoma and multiple myeloma, are not called metastatic cancer because they are thought to already be widespread when they are diagnosed.

A person diagnosed with cancer may never develop metastatic cancer. Whether or not a cancer spreads depends on many things including:

• the type of cancer
• how fast the primary cancer is growing and how likely it is to spread (the grade)
• the size and location of the primary cancer
• how long the primary cancer has been in the body
• if cancer treatments were used and how well they worked

Metastatic cancer may develop several years after the primary cancer is first diagnosed and treated. Sometimes cancer has already metastasized when it is diagnosed.

When cancer cells grow and divide, they can move from where they started to other areas of the body. There are 3 ways that cancer can spread.

Direct extension, or invasion, means that the primary tumour grows into tissues or structures around it. For example, prostate cancer can grow into the bladder.

Lymphatic system spread means that cancer cells break away from the primary tumour and travel to another part of the body through the lymphatic system. The lymphatic system is a group of tissues and organs that make and store cells that fight infection and disease.

Bloodstream spread, or hematogenous spread, means that cancer cells break away from the primary tumour, enter the blood and travel to a new place in the body.

The immune system usually attacks and destroys cancer cells that travel through the lymphatic system or blood. But sometimes cancer cells survive and settle in another area of the body, where they form a new tumour. To survive and grow in the new place, the tumour must form its own blood supply (called angiogenesis).

Cancer can spread anywhere in the body. Most cancers tend to spread to one place more often than others. For example, breast cancer and prostate cancer spread to the bones most often. Colorectal cancer tends to spread to the liver. Testicular cancer usually spreads to the lungs, and ovarian cancer usually spreads to the membrane that lines the abdomen (peritoneum).

Doctors may use the following terms to describe if cancer has spread or how far it has spread.

Localized means cancer is only in the area where it started and has not spread to other parts of the body.

Regional means the cancer has grown into surrounding tissues or organs, or it has spread to nearby lymph nodes.

Distant means the cancer is in a part of the body farther from where it started.

Doctors usually use the term metastatic cancer to describe cancer that has spread to distant organs or distant lymph nodes (called distant metastases). The most common places for distant metastases are the bones, brain, liver and lungs.

Cancer cells can also spread to the lining around the lungs (pleura), causing malignant pleural effusion, or to the peritoneum, causing malignant ascites.

Metastatic cancer is usually harder to treat than cancer that hasn't spread. In most cases, the goal of treatment for metastatic cancer is to help a person live as long as possible and maintain their quality of life. Treatments control and slow the growth of metastases, but the metastases usually don't go away completely.

Treatments that may be used for metastatic cancer include chemotherapy and other drug therapies, radiation therapy, surgery and ablation therapy. Treatments offered for metastatic cancer are based on several things, including where the cancer started, your symptoms, the location and amount of metastases, the treatments used for the original cancer, the goal of treatment, your overall health and what you prefer or want.

You will also be offered supportive therapies to be used in combination with treatments for metastatic cancer. Supportive therapies treat side effects of cancer treatments and symptoms of the disease, but they do not treat the cancer itself. Supportive care helps manage or prevent problems caused by the metastatic cancer. These therapies can also be called palliative treatments or palliative care.

Talk to your healthcare team. They can help you choose care and treatment for advanced cancer.

Clinical trials look at new ways to prevent, find or treat cancer. Talk to your doctor about clinical trials open to people with metastatic cancer in Canada. Find out more about clinical trials.