Explainer: What is cancer metastasis?

What is cancer metastasis?

Cancer metastasis refers to the spread of cancer cells beyond their original location, to other parts of the body.

What causes metastasis?

Metastasis occurs when cancer cells migrate from the primary tumor to another site via blood or lymph (more on the step-by-step process here).

The resulting new tumor is the same type of cancer as the original tumor. For example, if cancer cells from a breast tumor travel to the bone, the new tumor is called metastatic breast cancer, not bone cancer. This distinction has important implications for treatment as breast cancers have characteristics that differentiate them from cancers that originally arise in the bone.

Certain cancers are more likely to spread to specific areas of the body. Breast and prostate cancers have an affinity for bone whereas pancreatic cancers are more likely to spread to the liver or lung.

Cancers that metastasize may not always cause an immediate problem. Instead, they could lie dormant until a trigger causes them to reactivate and grow again. This is called “cancer recurrence.” The mechanisms behind recurrence are not clear, but scientists are hard at work to find out how and why this happens and to translate their findings into improved cancer care (you can read about one of these scientists, the Institute’s Dr. Xiaohong Li, and her work with prostate cancer and bone metastases here). 

Why is metastasis important?

Once cancer spreads, it becomes much more difficult to treat. That’s why early detection is key to preventing the spread of malignant cells. If caught early, medical intervention, such as surgical removal of the tumor or treatment with chemotherapy, may remove or kill cancer cells before they have time to travel beyond the original site.

Some treatments for metastatic cancer do exist, with most aiming to impede cancer cell growth and alleviate symptoms. Treatment options vary from person and person based on cancer type, exposure to previous therapies, medical history and several other factors (please remember, all treatment decisions should be made in close consultation with your physician).

How can research help?

Scientists are searching for new ways to prevent metastasis and to better treat it when it occurs through an improved understanding of how and why cancer cells spread. This will help scientists design:

  • More sensitive, precise detection methods: The earlier cancer is detected, the better the chances of successful treatment. Scientists are researching the minute, molecular variations that differentiate cancer cells from healthy cells, and cancer types and subtypes from each other (for more information on differentiating between cancers, check out this post). This knowledge will go a long way in helping create new, less invasive tests (such as blood tests).
  • Better, more targeted treatments: A detailed understanding of the mechanisms that cause cancer and allow it to spread helps scientists develop more effective treatments for these diseases with fewer side effects, giving people with metastatic cancer a chance for longer lives.