Prostate cancer tends to metastasize to bones as opposed to soft tissue and other organs. We have no idea why it does have a preference for bone, but it does.
Developing bone metastases in prostrate cancer is a very strong negative prognostic indicator. Prostate cancer’s tendency to favor bone over soft tissue causes significant morbidity and mortality for men. Bone metastasis has a major impact on quality of life and longevity for men with prostate cancer and it needs to be aggressively treated.
Because of this, prostate cancer survivors need to focus on drugs that slow down or interfere with the development of metastasis to the bone.
Currently, there are only three different treatments (drugs) that have been approved by the FDA for the treatment of bone issues for men with advanced prostate cancer. They are: zoledronic acid (Zometa), denosumab (Xgeva), and radium-223 dichloride (Xofigo).
Only the last, Radium-223 (Xofigo) has demonstrated the ability to prolong a man’s life, to extend survival.
The other two approved drugs, Zometa and Xgeva, do not extend life, but they have demonstrated a favorable impact on significant bone-related complications, such as fractures, the need for surgery, severe pain, and spinal cord compression, all serious conditions. Zometa and Xgeva improve the quality of life, they do not provide any life extension.
Radium-223 (Xofigo) is uniquely approved only for men with advanced castrate resistant prostate cancer. It is a radioactive isotope that is injected intravenously. It mimics calcium so it tends to migrate specifically to the bones where it delivers a short-range high-density alpha radiation to the bones, especially to the areas with a high cellular turnover that is characteristic of the bone metastases.
Because it mimics calcium, it is only effective for bone metastases; it doesn’t have any effect on cancer metastases in other organs or soft tissue, however it does a great job of shrinking the bone mets. And, as I mentioned it also extends survival.
Radium-223 is different than the two other drugs because it has an impact on the actual cancer biology, which results in an improved survival for men taking it. Zometa and Xgeva do not have an impact on the cancer biology and do not prolong life. These two drugs impact the bone proper. However, they still have a valuable role in the treatment of men with advanced prostate cancer because they improve the quality of life.
All three of these treatments have different mechanism of action, modes of administration, and come with different potential adverse events (side effects); however they all are important in the proper treatment of men with advanced prostate cancer.
They all need to be an intricate part of the treatment plan for any man with advanced prostate cancer.