What’s new in rhabdomyosarcoma research and treatment?
The treatment of rhabdomyosarcoma (RMS) has come a long way in the past few decades, largely due to the work of the Intergroup Rhabdomyosarcoma Study Group (now known as the Soft Tissue Sarcoma Committee of the Children’s Oncology Group). However, more work needs to be done. Research on RMS is being done at many medical centers, university hospitals, and other institutions across the world.
Better classification of rhabdomyosarcomas
Newer molecular techniques may help better categorize RMS and predict which patients will respond best to certain treatments. For example, rather than just looking at the cancer cells under a microscope, researchers have begun to use special genetic tests to help classify RMS.
About 1 out of 4 cancers that doctors would usually classify as alveolar rhabdomyosarcoma (ARMS) have been found to lack the typical gene change (the PAX/FOXO1 fusion gene) seen in ARMS. Some early studies have shown that these cancers seem to act more like embryonal rhabdomyosarcoma (ERMS) than ARMS. ERMS generally requires less intensive treatment than ARMS. If this finding is confirmed in other studies, it may allow doctors to use less intensive treatments on these cancers and still achieve the same results.
Improving standard treatments
A major goal of current research is to treat all patients more effectively, while reducing the need for intensive treatments (and their side effects) when possible. For example, researchers are studying whether children who have a low risk of the tumor recurring can be treated without using potentially harmful treatments such as radiation therapy and the chemotherapy drug cyclophosphamide.
Because children’s bodies are very sensitive to radiation, doctors are looking for ways to limit the doses as much as possible. Newer radiation therapy techniques allow doctors to aim the radiation more precisely, limiting the amount that reaches normal body tissues. Some of these techniques were described in the section “Radiation therapy for rhabdomyosarcoma,” and other approaches are now being studied.
For example, in stereotactic radiation therapy, a special machine aims high doses of radiation at the tumor from many different angles, concentrating it on the tumor very precisely for short periods of time.
Proton beam radiation is another newer approach. Standard radiation beams give off the same amount of radiation at all points in the body as they pass through it. Proton beam radiation uses radioactive particles that travel only a certain distance before releasing most of their energy. Doctors can use this property to limit the radiation reaching normal body tissues. This new approach seems promising, but it is not yet clear if it is better than other newer forms of radiation therapy. It is also available in only a handful of centers around the country at this time.
For patients at a high risk of tumor recurrence, doctors are looking at maximizing the early treatment with drugs such as cyclophosphamide and ifosfamide by giving them more frequently (a concept called interval compression).
Newer treatment approaches
Drugs that target specific parts of cancer cells (as opposed to just attacking fast-growing cells, as chemotherapy drugs do) are now being studied for use in RMS. Some of these drugs are already being used to treat certain adult cancers. Examples of newer targeted drugs being studied for use against RMS include:
- IGF-1 receptor inhibitors, such as cixutumumab (IMC-1A2)
- Drugs that affect a tumor’s ability to make new blood vessels, such as bevacizumab (Avastin) and sorafenib (Nexavar)
- Drugs that target the mTOR protein, such as temsirolimus (Torisel) and everolimus (Afinitor)
- Drugs that target the ALK protein, such as crizotinib (Xalkori)
- Drugs that target the cell’s hedgehog pathway, such as LY2940680 and LDE225
- Dasatinib (Sprycel)
Researchers are also testing other new ways to treat RMS. For example, some researchers are looking at exposing some of the body’s own immune system cells, called dendritic cells, to the abnormal PAX-FOXO1 protein that is found in many ARMS cells. The hope is that the dendritic cells will then cause the immune system to attack these cells, no matter where they are in the body.
Eventually, a combination of these approaches may prove to be the best way to treat RMS.
Last Medical Review: 08/13/2013
Last Revised: 08/13/2013