When cancer spreads: metastasis
Cancer usually starts as a tumor in an organ or tissue of the body — except for leukemia or lymphoma, where it affects the blood cells instead. When cancer spreads to other parts of the body beyond the area where it began, it is called metastasis (pronounced meh-TAS-tuh-sis). When cancer is found in an organ or tissue, it’s important to see if it has spread.
How metastasis happens
Cancer cells can sometimes “break away” from a tumor and enter the bloodstream. Cells can also go into the lymphatic system: This system normally fights infection and includes the lymph nodes, lymph vessels, and bone marrow. Cancer cells travel until they get stuck in a blood vessel or a lymph node; there, they start to grow, forming a new tumor.
When a cancer is aggressive (fast-growing), it may spread quickly. On the other hand, metastases can also show up months or years after the original cancer was found.
Where cancer spreads
When cancer spreads to lymph nodes near the original tumor, it is known as lymph node involvement or local disease. When cancer cells attack other organs or lymph nodes that are far away from the first tumor, it’s called metastatic cancer.
Cancer cells can spread to any part of the body; most often, though, they settle in the lungs, bones, liver, and brain. Where a cancer spreads usually depends on the type of cancer. For example, colon cancer tends to spread to the liver, because blood from the colon flows first to the liver. Lung cancer often moves to the brain or bones, while breast cancer may spread to the bones, lungs, liver, or brain.
Symptoms of metastatic cancer
Depending on where it’s found, metastatic cancer may or may not cause symptoms like pain or discomfort. Cancer that has spread to the bones can be very painful, though, and may cause bone fractures. Cancer in the brain can produce headaches or seizures. Shortness of breath may be caused by cancer that has spread to the lungs. Sometimes, when a tumor presses on nerves, it can also result in a lot of pain – some pancreatic and rectal cancers affect nerves in those areas. It’s important for patients to tell their doctors about any new or unusual symptoms, pain, or health issues, so that metastatic cancer can be ruled out.
When metastatic cancer does cause symptoms, it’s sometimes found before the original cancer.
How metastatic cancer is found and diagnosed
Metastasis is usually spotted by X-rays, scans (which include CT, MRI and PET scans) or a blood test. Doctors will also check a person’s blood, urine, or body tissues for tumor markers (special substances that are made by a tumor, or by a person’s body in response to a tumor). People with cancer may have different amounts of these markers in their blood, urine, or tissues than people without cancer.
To see if a cancer is new or has spread from a different site, a pathologist looks at a sample under the microscope. If the cancer has spread from another site, the cells will look the same as the original cancer: That’s why metastatic cancer is always named for the original tumor, no matter where it’s found. Breast cancer that has spread to the lungs is known as metastatic breast cancer, for example, not lung cancer.
Knowing how far a cancer has spread helps the medical team decide on the cancer’s stage and then choose the best treatment. (For more information, see the article Understanding Stages of Cancer.)
How metastatic cancer is treated
Even when cancer has spread, there are many ways to treat it — including the same treatments that may have been used for the original cancer:
- Chemotherapy: Drugs that are given by mouth or by injection, in order to “kill” cancer cells
- Radiation: High-energy rays that destroy tumors and cancer cells in a certain part of the body
- Surgery: Removal of tumors, cancerous tissue, and lymph nodes
- Biotherapy: Using part of the body’s own immune system, such as antibodies, to help fight the cancer
- Hormone therapy: Blocking hormones from helping in the growth of hormone-sensitive cancers, such as breast or prostate cancers
- Cryosurgery: Using extreme cold to destroy tumors
Treatments are usually chosen based on:
- The type of cancer
- The size and location of any cancer that has spread (metastasized)
- How the original cancer was treated.
It’s also important to treat symptoms that affect a person’s quality of life, like pain, fatigue, anxiety, or depression.
There has been a great deal of progress in cancer research over the last few years, with the introduction of many new treatments. As a result, the outlook for people with metastatic cancer may be getting better: It’s often possible to have a long, productive life, while still being monitored and/or treated for cancer.