Preventing and treating prostate cancer spread to bone

If prostate cancer grows outside of the prostate gland itself, it may first grow into nearby tissues or spread to nearby lymph nodes. After this, prostate cancer nearly always spreads to the bones next. Spread of cancer to the bones can be painful and can also result in other problems, such as fractures (breaks) or high blood calcium levels, which can be dangerous or even life threatening.

Preventing or slowing the spread of prostate cancer to the bones is a major goal of treatment if the cancer has grown outside of the prostate. If the cancer has already reached the bones, controlling or relieving pain and other complications is also a very important part of treatment.

Previously described treatments, such as hormone therapy, chemotherapy, and vaccines may help with this, but other treatments more specifically target cancer spread to the bones and the problems it may cause.

Bisphosphonates

Bisphosphonates are a group of drugs that can help relieve pain and high calcium levels caused by cancer that has spread (metastasized) to the bones. These drugs may also slow the growth of the metastases and help delay or prevent fractures. Bisphosphonates can also help strengthen bones in men who are receiving hormone therapy.

These drugs work by slowing down cells called osteoclasts. These cells normally break down the hard mineral structure of bones to help keep them healthy. But osteoclasts often become overactive when prostate cancer cells spread to the bones, which can cause problems.

The most commonly used bisphosphonate is zoledronic acid (Zometa^®), which is approved for use in bone metastases from prostate cancer. It is given as an intravenous (IV) injection, usually once every 3 or 4 weeks. Men given this drug are advised to take a supplement containing calcium and vitamin D to prevent problems with low calcium levels.

Other bisphosphonates have been approved for other uses, and some doctors use these "off label" (to treat a condition for which they have not been approved by the Food and Drug Administration) to treat prostate cancer.

Bisphosphonates can have side effects, including flu-like symptoms and bone or joint pain. They can also lead to kidney problems, so patients with poor kidney function may not be able to be treated with these medicines.

A rare but very serious side effect of bisphosphonates is osteonecrosis of the jaw (ONJ). With this condition, part of the jaw bone loses its blood supply and dies. This can lead to tooth loss and infections or open sores of the jaw bone that won't heal and are hard to treat. Some people develop ONJ after dental work (such as having a tooth pulled) is done while on this medicine. Many cancer doctors advise patients to have a dental checkup and have any tooth or jaw problems treated before they start taking a bisphosphonate. Maintaining good oral hygiene by flossing and brushing, making sure that dentures fit properly, and having regular dental checkups may also help prevent this condition.

Denosumab

Denosumab (Xgeva^®) is another drug that can help when prostate cancer spreads to bone. Like the bisphosphonates, denosumab also blocks bone cells called osteoclasts, but it does so in a different way.

In men whose cancer has already spread to the bones, denosumab can help prevent or delay problems like fractures. Studies have shown that it seems to work a bit better than zoledronic acid. It may also be helpful if zoledronic acid is no longer working.

In men with no obvious cancer spread to the bones but with rising PSA levels despite hormone therapy, denosumab may help slow the spread of the cancer to the bones. But it's not clear if it will help men live longer.

This drug is given as an injection under the skin every 4 weeks. Men given this drug are often urged to take a supplement containing calcium and vitamin D to prevent problems with low calcium levels.

Common side effects include nausea, diarrhea, and feeling weak or tired. Like the bisphosphonates, denosumab can also cause ONJ, so doctors recommend taking the same precautions (such as having tooth and jaw problems treated before starting the drug).

Corticosteroids

Some studies suggest that corticosteroid drugs (such as prednisone and dexamethasone) can help relieve bone pain in some men.

External radiation therapy

Radiation therapy can help reduce bone pain, especially if the pain is limited to one or only a few areas of bone. Radiation can be aimed at tumors on the spine, which can help relieve pressure on the spinal cord in some cases. Radiation therapy may also help relieve other symptoms by shrinking tumors in other parts of the body.

Radiopharmaceuticals

Strontium-89 (Metastron^®) and samarium-153 (Quadramet^®) are drugs that contain radioactive elements. They are injected into a vein and collect in bones. Once there, the radiation they give off kills the cancer cells and relieves some of the pain caused by bone metastases. About 4 out of 5 men with painful bone metastases are helped by this treatment at least for a while.

These drugs are especially helpful when prostate cancer has spread to many bones, since external beam radiation would need to be aimed at each affected bone. In some cases, one of these drugs can be used together with external beam radiation aimed at the most painful bone metastases.

The major side effect of this treatment is a lowering of blood cell counts, which could place you at increased risk for infections or bleeding, especially if your counts are already low.

Pain medicines

When properly prescribed, pain medicines (ranging from ibuprofen or acetaminophen to stronger opioids like morphine) are very effective. You may worry about addiction with opioids, but this is almost never a problem if the drug is being used as directed to treat cancer pain. Symptoms such as drowsiness and constipation are likely but can usually be treated by changing the dose or by adding other medicines.

If you have bone pain from prostate cancer, it is very important that it is treated effectively. This will help you feel better and allow you to focus on the people and activities that are most important to you. Don't hesitate to discuss pain, other symptoms, or any quality of life concerns with your cancer care team. Pain and most other symptoms of prostate cancer can often be treated effectively. If the treatments listed above don't help with symptoms, there are several other options.