When Cancer Spreads: Understanding Metastasis

By Louise Chang, MD

How does lung cancer reach other areas of my body? Why did breast cancer show up in my bones? What does it mean to have metastatic cancer?

It can be hard to understand how cancer starts in one place and also shows up in other places in the body that are far from where it started. The ability to spread, called metastasis, speaks to the aggressive nature of cancer and the challenge it poses.

Cancer starts from cells in our body that have gone rogue. The body has ways to monitor and dispose of abnormal cells that develop, but cancer cells are able to avoid the body’s defense system. They grow out of control and form into cancerous tumors.

As cancer cells multiply, they can get into the bloodstream and lymph system. This allows the cancer cells to travel and settle in other parts of the body. When cancer spreads like this, it is described as “metastatic” – because cancer cells have moved to a different location in the body. But metastatic tumors are still considered to be the same cancer type as where the cancer first started. This is why breast cancer that has spread to the bone or lungs is still breast cancer. Lung cancer that has spread to the liver is still lung cancer. [more]

Whether cancer is diagnosed at an early stage or more advanced stage, spread may occur despite best efforts in screening and treatment. When this happens, the approach to treatment will depend on a number of factors including the type of cancer, location, and extent of its spread, and a person’s overall health.

Each person’s case is different. Here are some questions you can ask your cancer care team or if you are getting a second opinion to help you understand your case and what to expect.

  • Where has the cancer spread?
  • Are there additional tests or exams that you recommend? If so, what are they and how often will I need them?
  • What symptoms or effects could I experience from the cancer now? What can we do to avoid or lessen them?
  • How will my treatment plan change? What are the options for treatment?
  • What are the benefits and risks of the treatment options?
  • What side effects can I expect from treatment? What can be done to help with side effects of treatment?
  • What is your experience with treating metastatic cancer?
  • Are you involved in clinical trials? Would you be able to help me look into clinical trials if I am eligible?

Researchers continue to study ways to curb cancer and its ability to spread. For example, researchers funded by the American Cancer Society are studying ways to stop the spread of breast cancer and skin cancer.

Learn more about metastatic cancer, how it is found, and how it is treated.


Dr. Chang is director of medical information for the American Cancer Society.

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