What`s new in bone metastasis research and treatment?

Scientists have learned a great deal about how cancer cells break off from a main tumor, spread through the blood and lymph systems, and begin to grow in a new location. Researchers are using this knowledge to develop new tests to find bone metastases and to develop therapies to prevent and treat bone metastases.

New imaging and lab tests

Newer imaging test may help better spot bone metastases before they cause problems. For example, a special kind of positron emission tomography (PET) scan for bone uses radioactive fluoride instead of glucose. The fluoride is attracted to bone metastases better than glucose. It is especially useful with newer devices that combine a computed tomography (CT) scan and a PET scan to help pinpoint tumors.

Studies are also being done on the types of substances released into the bloodstream when cancer cells start growing in bones. In the future, doctors may be able to know when cancer first reaches the bones so that metastases can be treated before they cause serious damage. Tests that detect substances released into the blood when cancer cells start growing in bones might also be used to find out if treatment for bone metastases is working.

Stereotactic body radiation therapy

A newer form of external radiation treatment, known as stereotactic body radiation therapy (SBRT), can deliver high doses of radiation therapy very precisely. It is being studied to treat cancers that have spread to bones in the spine because it might spare nearby important areas from getting much radiation.

Instead of giving small doses of radiation each day for several weeks, SBRT gives very focused beams of high-dose radiation on one or a few days. Several beams are aimed at the tumor from different angles. To target the radiation precisely, the person is put in a specially designed body frame for each treatment. Like other forms of external radiation, the treatment itself is painless.

Early results with SBRT have been promising. But because it is still a fairly new technique, there isn't much long-term data on its use.

New drugs to prevent and treat bone metastases

Researchers are looking for new drugs that target parts of bone cells such as osteoclasts (the cells that break down bone) and osteoblasts (the cells that help build bone) to try to slow the growth of bone metastases. Some compounds are already being tested.

An example of a newer drug that seems to slow these cells is cabozantinib. In early studies, this drug has been shown have an effect on several types of cancer that have spread to the bones. Larger studies are now under way to try to confirm these promising early findings.

Although not as close to being developed, researchers are looking for drugs that block the action of cancer cells on bone. Cancer cells put out chemicals that cause bones to dissolve. There are also compounds that allow the cancer cells to stick to bone and grow there. Some of these chemicals have already been identified. It is hoped that new drugs can be made to block them without harming the normal bone.

New radiopharmaceuticals

Radiopharmaceuticals are drugs that bring small amounts of radiation directly to tumors in bones. Some of these drugs are already being used, but doctors are now studying newer drugs that may be more effective and/or have fewer side effects. One example is radium-223 (Alpharadin), which uses a slightly different type of radiation from other drugs in this class. Study results in men with prostate cancer that has spread to the bones have been promising so far.

Researchers are also looking at new ways to deliver radioactive particles to cancer cells by attaching them to antibodies or certain chemicals.

Testing known drugs for new purposes

Clinical trials are now looking at some drugs already used to help treat bone metastases to see if they might also help prevent some cancers from spreading to bones. For example, bisphosphonates and denosumab are being studied as a possible way to prevent bone metastases in high-risk patients.