What Does Metastatic Cancer Mean?

The primary benefit of cancer screening is to catch cancers before they spread, or metastasize, and become more difficult to treat.

Almost any tumor can metastasize, although not all cancers do. For example, according to the Metastatic Breast Cancer Network, in developed countries such as the U.S., about 30 percent of women with early stage breast cancer will eventually develop metastatic breast cancer. Although tumors may spread to any part of the body, the most common sites for metastases are the lung, bones, and liver.

Oncologists name tumors based on the primary site of origin (such as breast or prostate, for example). When cancer cells spread, they are still the same type of tumor. The actual cancer cells don't change, they just move to a new location.

Think of the spread of cancer as a continuum. On one end of the continuum, cancer cells remain confined to the primary site. As you move along the continuum, tumor cells invade nearby tissue (local invasion) or move into the walls of lymph or blood vessels where they may travel to other parts of the body.

Once in motion, cancer cells may stop anywhere and once again invade local tissue. If the tumor continues to grow at the new site, it forms micrometastases. In some cases, the tumor stimulates the growth of new blood vessels, which deliver nutrients and help the cancer grow. However, just because cancer cells spread, does not necessarily mean they will form a new tumor.

There is no definitive diagnostic test for metastatic cancer. Diagnosing metastatic tumors depends on the type of primary cancer and the patient's symptoms. Some cancers, such as colon, ovarian, prostate, and testicular cancers, have biomarkers. Special blood tests measure the level of the marker and if it rises, it may indicate the tumor is active or progressing. Imaging tests and biopsies help oncologists determine where the cancer cells originated based on characteristics of the cell. If a patient was treated for cancer in the past, tumors at a new site are most likely metastases of the original cancer.

Usually metastasized cancer cannot be cured. Treatment, which is generally similar to treatment of the primary tumor, may help control the growth of the cancer and relieve symptoms.

When cancer metastasizes, oncologists classify it as stage IV, the most advanced type of cancer. Metastatic cancer is often more aggressive than the primary tumor. Patients who die from cancer generally die of metastatic cancer.

Sources:

National Cancer Institute. "Metastatic Cancer." Web. 23 May 2011.
http://www.cancer.gov/cancertopics/factsheet/Sites-Types/metastatic

Waknine, Yael. "One in 5 Patients With Metastatic Cancer Receives No Treatment." Medscape Medical News. Web. 12 June 2012.
http://www.medscape.com/viewarticle/765506

Cleveland Clinic. "Metastatic Cancer." Web.
http://my.clevelandclinic.org/disorders/diseases/metastatic_cancer/can_overview.aspx

Metastatic Breast Cancer Network. "Statistics for Metastatic Breast Cancer." Web.
http://mbcn.org/education/category/statistics/

National Comprehensive Cancer Network. "What is Metastasized Cancer?" Web.
http://www.nccn.com/component/content/article/54-cancer-basics/925-what-is-metastasized-cancer.html