Detailed Guide: Bone Metastasis

A Primer on Metastatic Cancer from the American Cancer Society

Metastatic cancer is cancer that has spread from the part of the body where it started (called its primary site) to other parts of the body. When cells break away from a cancerous tumor, they can travel to other areas of the body through either the bloodstream or lymphatic channels.

When the cells travel through lymphatic channels they can become trapped in lymph nodes, often those closest to the cancer's primary site. When the cells travel through the bloodstream they can go to any part of the body. Most of these cells die, but occasionally they don't. They settle in a new location, begin to grow and form new tumors. The spread of a cancer to a new part of the body is called metastasis.

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Even when cancer has spread to a new location, it is still named after the part of the body where it started. For example, if prostate cancer spreads to the bones, it is still called prostate cancer, and if breast cancer spreads to the lungs it is still breast cancer. A person with breast cancer that has spread to the bones is said to have breast cancer with bone metastases.

When cancer comes back in a patient who appeared to be free of cancer (in remission) after treatment, it is called a recurrence. Cancer may recur as:

   local recurrence (in or near the same organ it developed in); for example, a recurrence of breast cancer in the skin of the chest near where the original cancer was removed

   regional recurrence (in nearby lymph nodes or in the area that lymph nodes had been removed from)

   distant recurrence (involving any other part of the body not included in local or regional recurrence). Distant recurrence is also called metastatic recurrence. For example, the cancer might recur in distant parts of body such as in bones, the liver, or the lungs. This happens because some cancer cells have broken off from the original tumor, traveled elsewhere and begun growing in these new places.

Sometimes the metastatic tumors have already developed when the cancer is first diagnosed. In some cases, this metastasis is discovered before the primary (original) tumor is found. Sometimes a cancer can spread widely throughout the body before it is discovered without developing as a large tumor in the site where it started. When the original site cannot be determined, this condition is called cancer of unknown primary, and is discussed further in a separate American Cancer Society document.

Bone Metastasis: What It Means

Cancer cells that break off from a primary tumor and enter the bloodstream can reach nearly all tissues of the body. Bones are one of the most common sites for these circulating cells to settle in and start growing. Metastases can occur in bones anywhere in the body, but they are mostly found in bones near the center of the body.

Bone metastases are not the same as cancers that start in the bone, which are called primary bone cancers. Bone metastasis and primary bone cancers are very different. Primary bone cancer is much less common than bone metastasis. For information on primary bone tumors, refer to the American Cancer Society documents, Bone Cancer, Osteosarcoma, Multiple Myeloma and Ewing Tumors.

Bone metastasis is one of the most frequent causes of pain in people with cancer. It can also cause bones to break and high calcium levels in the blood (calcium is released from damaged bones). It also causes other symptoms and complications that can lower your ability to maintain your usual activities and lifestyle.

Many people with cancer (except for those with nonmelanoma skin cancer) may develop bone metastasis at some point in the course of their disease. It is the third most common site for metastases after lung and liver.

Breast, prostate, lung, kidney and thyroid cancers are most likely to spread to bones.

The spine is the part of the skeleton most commonly affected by bone metastasis. The next most common parts are the pelvis, hip, upper leg bones (femurs) and the skull.

Source: American Cancer Society

For more on cancer visit www.cancer.org