Prostate Cancer - What Is Bone Directed Therapy?

If prostate cancer spreads to other parts of the body, it targets and goes to the bones first. And, if the cancer has spread outside the prostate, preventing or slowing its spread to the bones is a major goal of treatment.
If the cancer has already spread to the bones, relieving pain and other complications is also a very important part of the cancer treatment. There are a number of ways and means to prevent and treat prostate cancer’s spread to bones.

Understanding them in detail

Bone metastasis or spread of cancer to the bone is an extremely painful condition. This can also cause fractures or potentially fatal conditions like high blood calcium levels. Bone-targeted treatments such as hormone therapy, chemotherapy, and vaccines are used but so are a slew of other treatments more specifically targeting bone metastasis and its side effects. These are:

1. Bisphosphonates: Bisphosphonates are drugs that work by slowing down the reproduction of bone cells or osteoclasts. These cells work by breaking down the hard mineral structure of bones to keep them healthy. These bone cells often become overactive when prostate cancer spreads to the bones.

Bisphosphonates can also be used:

• To help control and relieve bone pain
• To control the high calcium levels caused by prostate cancer metastasizing to bones
• To help slow the growth of cancer
• To help delay or prevent fractures
• To help strengthen bones in men on hormone therapy

Zoledronic acid or Zometa is the most commonly used bisphosphonate for prostate cancer. This is given as an intravenous (IV) injection, usually once every 3 or 4 weeks. The patients on this drug are also advised to take supplements containing calcium and vitamin D to prevent low blood calcium levels. Side effects include flu-like symptoms and bone or joint pain as well as kidney problems and sometimes osteonecrosis of the jaw (ONJ). In ONJ, part of the jaw bone loses its blood supply and dies, leading to tooth loss and infections of the jaw bone.

2. Denosumab: This is another drug that can help when prostate cancer spreads to bones. Like the bisphosphonates, denosumab also works by blocking osteoclasts. This drug is used:

• To help prevent or delay fractures
• To help slow the spread of cancer to the bones despite hormone therapy
• This drug is injected intravenously every 4 weeks.
• Common side effects include diarrhea, nausea, and fatigue.

3. Corticosteroids: These lower bone pain in some men in whom cancer has spread to the bones.
4. External radiation therapy: This helps if the pain is limited to one or only a few areas of bone. Radiation can also be aimed at tumors on the spine and other parts of the body.
5. Radiopharmaceuticals: These are drugs that contain radioactive elements and these are injected into a vein and go and settle in areas of damaged bones, where they give off radiation that kills cancer cells. The major side effects of these drugs is a decrease in blood cell counts which makes the body of the patient more prone to infections and bleeding.

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