Prostate cancers initially need the male hormone testosterone for growth. Hormone therapies that lower the level of testosterone are among the most effective treatments for prostate cancers that have spread to other organs (metastasized). The benefits of hormone treatments do not last, however. Over time, many prostate cancers continue to grow despite hormonal therapies (and are called “castration-resistant” prostate cancer).
The bones are a frequent site of metastasis for prostate cancer. When prostate cancer spreads to the bones, it can cause pain. In this study, researchers want to compare the effectiveness of the investigational drug cabozantinib (XL184) with standard therapy (mitoxantrone and prednisone) for reducing bone pain in men with previously treated castration-resistant prostate cancer. Cabozantinib blocks several proteins (called MET, RET, and vascular endothelial growth factor receptor 2) that help keep cancer cells alive. It is a capsule that is taken orally (by mouth).
In this study, patients will be randomly assigned to receive cabozantinib or mitoxantrone/prednisone, but not both. Investigators will also examine the effects of the two treatments on prostate cancer growth and the number of cancer cells circulating in the body.