Bones, lungs, and the liver are the most common places for cancer cells to spread, or "metastasize."
Once in the bone, these cancer cells can form new metastatic tumors. Do you then have bone cancer? No. You still have the type of cancer you were diagnosed with, except now it is metastatic. For example, breast cancer that spreads is known as "metastatic breast cancer." Metastatic cancers in the bone are also called bone metastases, or bone "mets."
Here are the types of cancer that are most likely to metastasize to the bone and what treatments can provide relief.
Bone Metastasis: Cancers that Commonly Spread to Bone
Bone metastasis is more likely with cancers such as:
About three out of four cases of bone metastasis result from tumors in the breast, prostate, lung, or kidney. Almost 70% of people with advanced breast or prostate cancer have bone metastasis; bone is commonly the first area of metastasis for these cancers.
How and Why Cancers Metastasize to Bones
The spread of cancer to bone is a complex process that doctors are just beginning to understand. It involves interaction between cancer cells and:
- The primary tumor (where the cancer began)
- The blood or lymph
- The bone
For metastasis to occur, cancer cells go through changes. First, they break away from the primary tumor. Then they enter the bloodstream or lymph system. (Lymph vessels are similar to blood vessels, but are part of the immune system.) Where the cancer cells travel may have something to do with where and how blood and lymph travels. Another factor may be how close the metastatic site is to the place where the cancer began.
Cancer cells appear to actually compete with stem cells for space in bone. Recent research with mice and prostate cancer has shown that these cancer cells may use the same signal to move to the bone as do blood cell-forming stem cells.
Once in the bone, the cancer cells must avoid attacks from the body's immune system. So they may go through more changes. This means the new tumor may be somewhat different from the primary tumor. This can make it more difficult to treat.
Why and Where Tumors Form in Bones
The type of cancer may have something to do with why tumors form in bones. Certain cancers may release proteins that affect how a tumor forms.
Bones provide fertile ground for the growth of tumor cells because they are areas of constant cell turnover and growth. And bone cells release substances that may prompt faster cancer growth. Cancer cells may also attach better to bone than to other substances in the body for some reason.
Which bones do cancers tend to spread to?Cancer cells can go anywhere, but they often go to the bones with the greatest blood supply. This includes bones in the:
- Upper arms