What is metastatic cancer?
Cancer can 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, or secondary, 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. The term metastatic cancer is usually only used to describe solid tumours that have spread to another part of the body. Some cancers, such as leukemia, lymphoma and multiple myeloma, are considered widespread when they are diagnosed and so are not referred to as metastatic cancer.
A person diagnosed with cancer may never develop metastatic cancer. Whether or not a cancer spreads depends on many factors including:
- the type of cancer
- the grade of the primary cancer
- the size and location of the primary cancer
- how long the primary cancer is 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. 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 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 diseases.
Bloodstream, or hematogenous, spread means that cancer cells break away from the primary tumour, enter the bloodstream 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 bloodstream. 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 location, 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 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 sites of distant metastases are the bones, brain, liver and lungs.
Metastatic cancer is usually more difficult to treat than cancer that hasn’t spread. In most cases, the goal of treatment for metastatic cancer is to prolong survival and maintain quality of life. Treatments control and slow the growth of metastases, but the metastases usually don’t go away completely. Treatments are also used to manage or prevent problems caused by the metastatic cancer (called supportive therapies).
Treatments offered for metastatic cancer are based on several factors, including where the cancer started, symptoms, location and amount of metastases, treatments used for the original cancer, the goal of treatment, your overall health and your personal preferences.
Treatments that may be used for metastatic cancer include chemotherapy and other drug therapies, radiation therapy, surgery and ablation therapy. A combination of different treatments and supportive therapies is often used.
Clinical trials are research studies that test new ways to prevent, find, treat or manage cancer or other diseases. Clinical trials for metastatic cancer may be available. If you want to take part in a clinical trial, talk to your doctor or healthcare team to find out if you are eligible. Find out more about clinical trials.
A description of a tumour that includes how different the cancer cells look from normal cells (differentiation), how quickly the cancer cells are growing and dividing, and how likely they are to spread.
Grades are based on different grading systems that are used for specific cancers. Some types of cancer do not have a specific grading system.
The process of examining and classifying tumours based on how cancer cells look and behave under the microscope is called grading.
The group of tissues and organs that produce and store cells that fight infection and diseases.
The lymphatic system includes the adenoids, tonsils, spleen, thymus, lymph nodes, lymph vessels and bone marrow.
Also called the lymph system.
The complex group of cells and organs that defend the body against infection, disease and foreign substances.
The membrane that lines the walls of the abdomen and pelvis (parietal peritoneum), and covers and supports most of the abdominal organs (visceral peritoneum).
I’m extremely grateful to the Canadian Cancer Society for funding my research with an Innovation Grant.
How can you stop cancer before it starts?
Discover how 16 factors affect your cancer risk and how you can take action with our interactive tool – It’s My Life! Presented in partnership with Desjardins.