When prostate cancer cells spread to the bone, this is known as prostate cancer bone metastases (not “bone cancer”). Bones are the most common site of prostate cancer metastasis, occurring in 85%–90% of patients with metastatic prostate cancer. Once the cells settle in the bone, they start to interfere with the bone’s normal health and strength, often leading to bone pain, fracture, or other complications that can significantly impair a man’s health.
Early detection of bone metastases can help determine the best treatment strategy. It can also help ward off complications. Because men with prostate cancer bone metastases often experience painful episodes, pain management and improving quality of life are important goals of treatment.
Treatments
Treatment with bisphosphonates or denosumab can help prevent complications related to bone metastases, like fractures. Bisphosphonates are drugs that are designed to help reset the balance in the bone between bone growth and bone destruction which is disrupted by the prostate cancer bone metastases.
Zoledronic acid (Zometa) is a bisphosphonate 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. Less frequent schedules are sometimes used as well depending on your individual circumstance and risk.
Denosumab (Xgeva) is a different type of bone-targeting drug which is given as an injection, rather than an infusion, and may be used instead of a bisphosphonate.
There are some risks with both classes of bone-targeted agents, including something called osteonecrosis of the jaw (ONJ) that can occur after deep dental procedures and extractions or sometimes spontaneously. This results in sometimes jaw pain and poor healing of your teeth. Certain laboratory assessments must be monitored with regular use of either medication. Daily calcium and vitamin D are supplements are typically recommended, and you should discuss this with your doctor.
Painful bone metastases can commonly be treated successfully with external beam radiation therapy. This generally involves 1-2 weeks of daily radiation treatments and can significantly improve symptoms. Sometimes radiation therapy may be recommended if there is an area of the bone (typically in the hip or leg) which looks like it may easily break, even if it is not currently painful. The goal in that case is to reduce the risk of developing a fracture. This kind of radiation targeted to sites of painful metastases can usually be safely given, even if you received radiation to treat your initial prostate cancer.
If there are multiple spots are involved, a medication called radium-223 (Xofigo®) can be used. This is a radiopharmaceutical that is chemically similar to calcium. Because of its calcium-like chemical properties, radium-223 is absorbed in areas where bone is actively growing and healing. Treatment with radium-223 both prolongs survival and improves quality of life, with more time free of the debilitating complications of advanced prostate cancer. It is important to discuss with your doctor the proper sequence of available therapies. Studies have shown that patients with predominantly bone-only metastatic disease do better when radium-223 is given earlier in the course of the disease than when it is given after many lines of therapy (e.g., enzalutamide, chemotherapy, abiraterone).
Guidelines do not recommend that radium-223 be used simultaneously in combination with abiraterone acetate and prednisone/prednisolone or enzalutamide outside of a clinical trial, as this combination was associated with an increased risk for bone fractures. If these medications are given in combination, patients should receive a medication to improve bone density to prevent fractures, such as zoledronic acid or denosumab.
Complementing radiation treatments with medications (opiates, non-steroidal anti-inflammatory medications), alternative medicines (acupuncture, healing touch, yoga, biofeedback), and psychological and social support is recommended.
Chemotherapy can also be highly effective in reducing bone pain.
Learn more about general bone health while on hormone therapy here.