Cancers that start in an organ can spread (metastasize) to other parts of the body, including the bones. Cancers that spread to the skeleton are called bone metastases or bone-related events (SREs). Bone metastases can cause pain and may lead to fractures and other health problems, such as spinal cord compression and excess calcium in the bloodstream (hypercalcemia).
It is not clear why some cancers spread to bone and not others. But doctors know that certain types of cancer—such as breast, prostate, and lung cancers—are more likely to spread to the bones than other types of cancer.
The earliest sign of bone metastasis is often a sudden, new pain that feels similar to arthritis or a muscle strain. The pain may come and go, but it usually gets worse over time. Over time, the metastasis may lead to broken bones or other health problems such as excess calcium in the bloodstream (hypercalcemia). The skeleton is also one of the most common sites for cancers to spread to from the liver and lungs.
Bone metastasis is most commonly seen in the spine (vertebrae), pelvis, upper leg bone (femur), humerus, and ribs, but it can occur in any bone in the body. The most common type of bone metastasis is osteolytic, which means that cancer cells break down the bones and release the mineral into the bloodstream. This makes the bone softer and weaker, which increases the risk of breaking or other complications.
X-rays are the most common test used to detect bone metastasis, but a doctor may order other tests or scans to find out more about what is causing the pain and to determine how advanced the metastases are. These include a CT or an MRI scan, which take detailed pictures of the bones, or a PET scan, which uses radio waves and strong magnets to make a 3-dimensional picture of the body.
If a biopsy is needed to confirm the diagnosis, a small sample of tissue from the bone lesion will be taken and looked at under a microscope. This can tell doctors what type of cancer the bone tumor is and whether it is localized or metastatic.
A doctor can treat bone metastasis with medication, radiation therapy, and surgery. Some of the medications, such as chemotherapy, hormone therapy, and targeted therapies, can help control the primary cancer and also kill the bone metastasis cells. These medicines can also reduce pain and prevent further damage to the bone. Other medicines, such as bisphosphonates and denosumab, can help make the bone stronger and prevent fractures.
Surgery is sometimes done to help reduce pain or to stabilize a weakened bone. Screws, plates, pins, and rods can be put into the bone to hold it together. Surgery should not be rushed or the first choice of treatment.
Research is continuing to explore the ways that cancers spread to bone and how to better manage these metastases. It is important for people to stay in touch with their physicians and to bring any new symptoms to the attention of their physician right away.
