Although many cases of prostate cancer are easily cured, a small subset of patients unfortunately develop an advanced disease that is difficult to treat. When prostate cancer spreads, it does so either in a local or distant fashion. If local, it can spread to lymph nodes, beyond the prostate to adjacent organs or to lymph nodes in the pelvis. When prostate cancer spreads distantly to bone, the prognosis is more severe and a cure can often not be achieved.
When prostate cancer spreads to bone, the first-line treatment is usually hormonal manipulation. Medications are given that eliminate the male hormone testosterone. Without testosterone, prostate cancer tends to stop growing and the disease comes under control. During this phase of therapy, most of the symptoms that are associated with advanced disease tend to dissipate. Pain that arises as a result of the disease spreading to bone tends to drastically improve. However, many patients do not respond to the hormonal deprivation therapy, and may develop castrate resistant prostate cancer (CRPC).
Patients who develop this form of prostate cancer have several drugs available for treatment. The newer agents include Provenge (sipuleucel-T), an agent that stimulates an immune response, Zytiga (abiraterone) an agent that block androgen synthesis, and Xtandi (enzalutamide), a drug that binds and inhibits the androgen receptors. However, none of these drugs directly address the bone metastasis.
Recently, Xofigo has been approved for the treatment of patients who have castrate resistant prostate cancer. Xofigo - radium-223 - is a bone-seeking radionuclide that has been shown to control pain in prostate cancer that is metastatic to bone. This substance binds to minerals in bone and emits radiation to areas of increased bone turnover. Recently published data form a phase III trial that compares this substance to a placebo in symptomatic patients with castrate resistant prostate cancer demonstrates a significant improvement in the median overall survival, up to 3.6 months for patients that completed six cycles of the drug. The treatment also resulted in a decrease in the number of bone fractures that occurred in this group of patients.
This new agent offers new promise for those patients with castrate resistant disease that otherwise does not respond to the available drugs. Treatment with this drug has minimal side effects and is extremely well tolerated by patients. With this new addition to the armamentarium of medications that are available for patients who have castrate resistant prostate cancer, patients now have more hope than ever for longer survival and a better quality of life.