Treating Metastases

An important part of prostate cancer bone metastases management is maintaining adequate calcium and vitamin D levels and exercising regularly. Even though none of these are treatments for bone metastases, they will all help to maintain strong bones and help to minimize bone loss and osteoporosis, which can make treating bone metastases more challenging.

Radiation Therapy Targeting Bone Metastases

Men who experience pain from a bone metastasis will often be treated with radiation targeted directly to the metastasis. This will kill the prostate cancer cells and relieve the pain. (Note that radiation therapy used to treat bone metastases is completely unrelated to radiation therapy that might have been used earlier in prostate cancer treatment.)

External beam radiation therapy uses x-rays to kill the cancer cells that have settled in the bones. This type of treatment, sometimes referred to as spot radiation, is mapped out and planned very precisely by the radiation oncologist to ensure that the x-rays are targeting the metastasis and are not causing damage to the surrounding bone and muscle tissue.

Radiopharmaceuticals, or radioactive drugs, are injected into the body through a vein and settle in the bone metastases, at which point they release radiation to the local area and kill the cancer cells. The two drugs used for this procedure, samarium (Quadramet) and strontium (Metastron), are sometimes used in combination with chemotherapy.

Bone-Targeting Agents (Bisphosphonates)

Under normal circumstances, bone cells are destroyed and created at a constant rate. Increasing the activity of osteoblasts, cells that form new bone cells, ultimately results in an overgrowth of bone tissue; increasing the activity of osteoclasts, cells that destroy bone cells, ultimately results in porous, brittle bone tissue. In men with prostate cancer bone metastases, both of these processes occur at faster than normal rates, leading to both an overgrowth of bone tissue and weakened and brittle bones. The combination of these two processes makes the bones unstable, and therefore prone to fracture.

Bisphosphonates are drugs that are designed to help reset the balance in the bone between bone growth and bone destruction. Zoledronic acid (Zometa) is a bisphosphonate given intravenously that can delay the onset of complications associated with prostate cancer bone metastases and relieve pain. It is typically given once every three weeks as a 15-minute infusion.

Other bisphosphonates are sometimes used in men with prostate cancer to prevent or slow bone loss while taking hormone therapy. These drugs, alendronate (Fosamax) and risedronate (Actonel), are given in pill form, and are also used to counteract the bone loss of osteoporosis in postmenopausal women or in women who are taking hormone therapy for breast cancer.

Additional Reading:

Chapter 8: Managing Bone Metastases and Pain