Bone Metastasis

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What is metastasis?

When cancer spreads from the part of the body where it started (its primary site) to other parts of the body it is called metastasis. Metastasis can occur when cells break away from a cancerous tumor and travel through the bloodstream or through lymph vessels to other areas of the body. (Lymph vessels are much like blood vessels, except they carry a clear fluid called lymph back toward the heart.) Cancer cells that travel through the blood or lymph vessels can spread to other organs or tissues in distant parts of the body.

Many of the cancer cells that break off from the original tumor die without causing any problems. But some settle in a new area. There, they begin to grow and form new tumors. When cancer spreads, we say that it metastasizes. If there is only a single tumor, it’s called a metastasis or a metastatic tumor. When there are 2 or more metastatic tumors, it’s called metastases.

Sometimes metastatic tumors are found by tests done when the primary cancer is first diagnosed. In other cases, the metastasis is found first, causing the doctor to look for the place that the cancer started.

Sometimes, no metastases are seen when the cancer is first found. Instead, they are found later, after the patient has been treated and was thought to be cancer free. When a cancer has come back after treatment, it’s called recurrence. Recurrence is not the same as metastases – it can also occur at or near the place the cancer started. When it does come back as metastases, it’s called a distant recurrence. For a cancer to recur as metastatic disease, some cancer cells had to have broken off from the primary tumor and survived the initial treatment. These cells traveled through the body and started growing in new places.

Different cancers tend to spread to different sites, but some of the most common sites of distant recurrence include the bones, liver, brain, and lungs.

What does it mean when you have bone metastases?

Bone is the supporting framework of the body. Bones are made of cells, a network of fibrous tissue called matrix, and minerals such as calcium that attach to the matrix and give the bone its strength and hardness.

The bone contains 2 main kinds of cells. The osteoblast is the cell that forms new bone, and the osteoclast is the cell that dissolves old bone. New bone is always forming while old bone is dissolving. This helps keep the bones strong.

Knowing a little about these 2 kinds of cells can help you understand how bone metastases grow, and how some medicines work to treat bone metastases.

Although cancer can spread to nearly all tissues of the body, one of the most common sites of cancer spread is the bones. Areas of cancer spread in the bones are called bone metastases.

Some cancers start in the bone, rather than spreading to the bones from somewhere else. Cancers that start in the bone are called primary bone cancers. These cancers are very different from bone metastases. Bone metastasis is actually much more common than primary bone cancers, especially in adults.

This document is only about bone metastasis. If you would like information on primary bone cancers, see our documents called Bone Cancer, Osteosarcoma, and Ewing Family of Tumors.

Many people with cancer will develop bone metastases at some point in their disease. Bones are often a site of metastases for certain common tumors, such as breast and prostate cancers.

Metastases can occur in any bone in the body, but are most often found in bones near the center of the body. The spine is the most common site of bone metastasis. Other common sites are the hip bone (pelvis), upper leg bone (femur), upper arm bone (humerus), ribs, and the skull.

Once cancer has spread to the bones or to other sites in the body it is rarely able to be cured, but often it can still be treated to shrink, stop, or slow its growth. Even if a cure is no longer possible, treating the cancer may be able to help you live longer and feel better. Other treatments can help prevent or manage cancer symptoms. (See the section called “How are bone metastases treated?”)

Last Medical Review: 02/07/2014
Last Revised: 02/17/2014