What Is Bone Metastasis?
Bone metastasis happens in people who have cancer that forms in another part of the body. Cancer cells from that area break away and travel through the bloodstream and lymphatic system. When the cancer spreads to distant body organs, this is called metastasis. Common sites of metastasis include bones, the lungs, and the liver.
Any type of cancer can raise the risk for bone metastasis. Although your doctor can't tell for sure if cancer will spread, certain types of cancer are more likely to spread to bone. These include cancers of the breast, lungs, thyroid, prostate, and kidneys. Larger tumors that have spread to the lymph nodes are also more likely to spread to the bones.
Where Bone Metastases Form
A bone metastasis can grow in any bone. But cancer most commonly spreads to the bones that are close to the center of the body. The spine is the most common place for a bone metastasis to form. Other common areas for bone metastases include the thigh bone, upper arm bone, ribs, hips, and skull.
Bone pain is often the first symptom of a bone metastasis. At first, the pain may come and go. It is often worse at night but feels better when you move. Over time, the pain may feel worse with movement and become more constant.
Cancer growing in the spine can put pressure on the spinal cord. This can affect the nerves, causing loss of mobility, muscle weakness, numbness, and trouble urinating. Cord compression is a medical emergency because it can lead to paralysis. Treatments include steroid injections, radiation, chemotherapy, and surgery. Physical therapy may be needed to help regain muscle tone.
How Metastasis Affects the Bones
Bone metastasis often damages bones by making them weaker. Over time, this can cause them to break, even during routine activities like coughing or sitting down in a chair. At other times, bone metastasis can cause bone to become harder, though it may still break. In some cases, bone metastases can have both types of features.
Imaging Tests for Bone Metastases
Your doctor may order imaging tests to see if the cancer has spread to the bones, even if you haven't noticed any symptoms. These tests look at the inside of the body. X-rays may help find areas of bone metastases and confirm if a bone is broken. A bone scan can often find metastases earlier than an X-ray, and can check the whole body at once. CT scans, MRI scans, and PET scans also can show cancer that has spread.
Lab Tests for Bone Metastases
As bone metastases damage bone, calcium is often released from the bone into the bloodstream. High calcium levels can be a serious problem and can lead to nausea, constipation, dehydration, and even coma. Your doctor may send a tissue sample from the bone to a lab to confirm bone metastases.
Treating the Primary Cancer
Chemotherapy and hormone therapy target the main cancer. Taken by mouth or injection, they attack any cancer cells in the body. These treatments, called systemic because they affect the whole body, can cause side effects such as nausea, vomiting, fatigue, hair loss, and increased risk of infection.
Bisphosphonates are a class of drugs that treats weak bones. They can be used to treat osteoporosis, a condition in which the bones get thin and weak. In certain cancer patients, bisphosphonates may help curb bone pain, reduce bone damage, lower elevated calcium levels, and decrease the risk for broken bones. Side effects include fatigue, nausea, vomiting, anemia, and bone or joint pain. A serious but rare side effect is jawbone death.
Treating Just the Bones
Local treatments focus on just the bone or bones where the cancer has spread. They work by destroying the tumor or slowing down the growth of the cancer cells. External beam radiation uses high-powered energy rays to kill cancer cells. It is similar to an X-ray, but much stronger. Ablation is another local treatment that destroys tumors with cold, heat, electric currents, or alcohol. Ultrasound may also be used to destroy nerve endings in the bone around the tumor. Another local treatment involves injecting bone cement to help stabilize the area.
Surgery is often used as a treatment to help stabilize weakened bone that may be at risk for breakage. Your doctor may insert rods, screws, pins, or plates to help stabilize a bone and keep it from breaking. Surgery is also used to repair broken bones. But broken bones due to cancer often don't heal well. Your doctor may focus on trying to prevent bones from breaking in the first place.
In many cases, treatments for bone metastasis will also help relieve bone pain. But if pain persists, your doctor may suggest over-the-counter pain relievers, such as acetaminophen, ibuprofen, or naproxen. If these medications don't bring relief, your doctor may prescribe a stronger pain reliever, such as codeine, hydrocodone, oxycodone, or morphine.
Bone metastases aren't usually curable, but treatments may be able to shrink them and relieve symptoms. Talk to your health care provider about any new symptoms or side effects you've noticed. You may have a quicker recovery if you take an active role in your health -- by asking questions, learning more about your condition and its treatments, and taking care of yourself. Talk to your doctor about other treatment options that may be right for you.