Bone metastasis occurs when cancer cells spread from their original site to a bone. Nearly all types of cancer can spread (metastasize) to the bones. However there are some types of cancer that are more prone to spread to bone, including prostate cancer. The most common sites of bone metastasis are the vertebrae (bones of the spine), ribs, pelvis (hip bone), sternum (breastbone) and skull. Sometimes only one area of bone is affected. Sometimes metastasis develops in several bones at the same time.
What Causes Bone Metastasis
Cancer cells sometimes break away from the original tumor and go to a blood or lymph vessel. Once there, they move through your body. The cells stop in capillaries — tiny blood vessels — at some distant location. The cells then break through the wall of the blood vessel and attach to whatever tissue they find. They multiply and grow new blood vessels to bring nutrients to the new tumor. Prostate cancer prefers to grow in specific areas, such as lymph nodes or in the ribs, pelvic bones, and spine.
The symptoms of bone metastasis vary depending on which and how many bones are affected. Once cancer cells have spread to the bones, you may experience symptoms such as:
- bone pain
- weak bones, increasing your risk for fractures
- spinal cord compression and related weakness or numbness
- high blood calcium levels
- stiffness or pain in the hip, thighs, or back
These symptoms can cause severe discomfort and disability. Spinal cord compression can also result in nerve damage, which can lead to muscle weakness or paralysis, numbness in the legs or arms, or loss of control of bladder and bowel functions.
Diagnosing Bone Metastasis
The following tests may be used to diagnose bone metastases. Many of the same tests can help your healthcare team plan treatment and monitor bone metastases. These tests include:
- Health history and physical exam
- Blood tests
- Imaging tests such as an X-ray and a MRI
A healthcare team will create a treatment plan just for you. It will be based on your needs and usually includes a combination of different treatments. Treatments can control and slow the growth of bone metastasis, but the metastasis will usually not go away completely. Treatments can also manage or prevent problems caused by bone metastases. Treatments include:
Bisphosphonates – Can prevent the thinning of the bone and help make them stronger. Zometa (zoledronic acid) is the most commonly used bisphosphonate and is usually given once every four weeks by an intravenous infusion through a vein.
Radiation – There are several types of radiation therapies that can be used to treat and manage the cancer and the pain it can cause when it grows in the bones. While these types of therapies will not eliminate all cancer cells or cure the cancer, they do relieve bone pain and can slow the growth of cancer.
Radiopharmaceuticals – Radiopharmaceuticals are drugs that contain radioactive elements. They are injected into a vein and settle in areas of damaged bones (like those containing cancer spread). Once there, they give off radiation that kills cancer cells. These drugs can be used to treat prostate cancer that has spread to many bones. Unlike external beam radiation, these drugs can reach all the affected bones at the same time.