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When cancer cells spread to the bones (bone metastases), they can cause many problems such as pain, broken bones, or more serious problems. Almost all cancers can spread to the bone, but cancers that often spread there include breast, lung, prostate, kidney, melanoma, ovarian, and thyroid. The spine is the most common site for bone metastases. Other common sites are the hip bone (pelvis), upper leg bone (femur), upper arm bone (humerus), ribs, and the skull.

Normally, bone is maintained by 2 kinds of bone cells.

• Osteoblasts form new bone
• Osteoclasts break down old bone

When these cells are both working the way they should, new bone is always forming while old bone is being broken down. This helps keep the bones strong.

When cancer cells spread to the bone, they block or speed up the action of the osteoblasts and osteoclasts, too much bone is broken down or too much bone is made. Either of these changes can make bones break easier than normal.

Bone metastases (mets) can cause other problems as well:

• When cancer spreads to the bones of the spine, it can press on the spinal cord. This can cause nerve damage that may lead to paralysis if not treated right away.
• As too much bone dissolves, calcium is released into the blood. This can lead to problems caused by high blood calcium levels (hypercalcemia).

Signs and symptoms of bone metastases

It’s very important to tell your cancer care team about any new symptoms you have. Finding and treating bone metastases early can help prevent problems later.

Pain

Bone pain is often the first symptom of cancer that has spread to the bone. The pain may come and go at first. It tends to be worse at night and may get better with movement. Later on, it can become constant and may be worse during activity. The bone might be so weak that it will break. This can often be prevented if the bone metastasis is found early.

There are many ways to treat pain caused by bone metastases. The treatment will depend on the type of cancer as well as the number and location of bone metastases. Sometimes treatment being used to treat the main (primary) cancer will help shrink the metastases. Other times, medicines made to stop the effects of the cancer on the bone may be given (See Drugs to treat bone metastases below). In addition, some more local treatments, like radiation therapy or even surgery, can help relieve the pain.

Pain medicines are also very helpful. Many kinds of pain medicines are used to treat cancer pain. There are also a lot of ways the medicines can be taken, such as pills, patches, and pumps that let you put the medicine into your body when you need it.

Fractures (broken bones or breaks)

Breaks might happen with a fall or injury, but a weak bone can also break during normal activities. These breaks often cause sudden, severe pain. Fractures most often happen in the long bones of the arms and legs and the bones of the spine. Sudden pain in the middle of the back, for instance, may mean a bone in the spine has broken.

When possible, your doctor will try to prevent the fracture. Medicines may be given to try and strengthen the bones which can help prevent fractures (see Drugs to treat bone metastases below). Cancer in the bone may cause severe pain for a while before the bone breaks. If an x-ray shows an arm or leg bone is likely to break, surgery may be done to put a metal rod in the weak part of the bone.

If the bone has already broken, surgery is usually done to put a steel support over the broken part of the bone. If bones of the spine break, a bone cement might be injected into the damaged bones (vertebroplasty or balloon kyphoplasty). This can help support the bone.

Radiation treatments may be given after surgery to try to prevent any more damage. The radiation won’t make the bone stronger, but it might stop further damage.

If you feel confused, dizzy, or weak, talk with your cancer care team about safety equipment you can use at home, such as shower chairs, walkers, or handrails.

Spinal cord compression

Cancer growing in the bones of the back can press on the spinal cord.  One of the earliest symptoms of spinal cord compression is pain in the back or neck.

If a spinal cord compression isn’t treated right away, the person can become paralyzed. Most often this affects the legs (so that the person can’t walk) but if the tumor is pressing on the spinal cord in the neck, the arms and the legs can be affected.

Spinal cord compression can show up in different ways:

• Back pain (sometimes with pain going down one or both legs)
• Numbness of the legs or belly
• Leg weakness or trouble moving your legs
• Loss of control of urine or stool (incontinence) or problems passing urine

If you notice symptoms like these, call your doctor right away or go to the emergency room.

If the cancer is just starting to press on the spinal cord, treatment can help prevent paralysis and help relieve the pain. Radiation is often used as part of the treatment, sometimes with a type of medicine called a steroid or corticosteroid. The radiation often is started right away, within the first 12 to 24 hours.

If the spinal cord is already showing signs of damage (such as weakness in the legs), immediate surgery followed by radiation may be the best treatment. This may allow a patient to walk and function better than if they get radiation alone. People with very advanced cancer or other serious medical problems may not be able to have this kind of surgery.

High blood calcium levels

When cancer spreads to the bones, too much calcium from the bones can be released into the bloodstream. This is called hypercalcemia.

High blood calcium levels can cause problems such as

• Constipation
• Passing urine often
• Feeling sluggish or sleepy
• Feeling thirsty all the time and drinking lots of liquids
• Muscle weakness
• Muscle and joint aches
• Confusion
• Coma
• Kidney failure.

Treatment includes giving large amounts of intravenous (IV) fluids to protect the affected kidneys and medicines such as bisphosphonate drugs (see below) to bring blood calcium levels down quickly. Once the calcium level is back to normal, treating the cancer can help keep the calcium level from getting too high again.

How are bone metastases found? ?

Bone mets may be seen on imaging tests that take pictures of the body. Some common imaging tests used to check for bone mets include: 

• X-ray
• CT or CAT scan
• MRI
• PET scan
• Bone scan

Bone mets may be found because a person is having pain, or if the doctor is looking to see if the cancer has spread anywhere else in the body. Sometimes, a bone biopsy may also be done.?

Drugs to treat bone metastases

The drugs used most often for treating bone problems in people with bone metastases are the bisphosphonate drugs pamidronate (Aredia) and zoledronic acid (Zometa) and the drug denosumab (Xgeva). These drugs are given intravenously (IV or into a vein) or subcutaneously (under the skin). Most patients are treated once a month at first, but may be able to be treated less often later on if they are doing well. Treatment with one of these drugs can help prevent further bone damage and events related to weakened bones such as fractures, hypercalcemia, and spinal cord compression.

These treatments can have a rare but serious side effect called osteonecrosis of the jaw (ONJ). Patients complain of pain and doctors find that part of the jawbone has died. This can lead to an open sore that doesn’t heal or tooth loss in that area. The jawbone can also become infected. Having jaw surgery or having a tooth removed can trigger this problem. It is best to avoid these procedures while you are taking one of these medicines. One way to avoid these dental procedures is to maintain good oral hygiene by flossing, brushing, making sure that dentures fit properly, and having regular dental checkups. Any tooth or gum infections should be treated right away. (Dental fillings, root canal procedures, and tooth crowns do not seem to lead to ONJ.) If ONJ does occur, the doctor will stop the bone medicine.

Your doctor will probably recommend that you have a dental checkup before starting treatment. That way, any dental problems can be taken care of before starting the drug. They might also recommend taking calcium and Vitamin D supplements while on the medicine to help your body build bone.