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Advanced type of cancer radiation reduces side effects, but impact on cancer control is unclear

An advanced type of cancer radiation is more successful than traditional radiation in avoiding "dry mouth" when treating head and neck cancers. However, it is unknown whether the treatment is better or worse at reducing the size of tumors, according to a new comparative effectiveness review funded by the Agency for Healthcare Research and Quality (AHRQ). The report finds that intensity-modulated radiation therapy (IMRT) leads to fewer cases of xerostomia, commonly known as dry mouth, than other types of radiation. Xerostomia occurs from damage to the salivary glands, and can affect basic functions like chewing, swallowing, and breathing; senses such as taste, smell, and hearing; and can significantly alter a patient's appearance and voice. However, the report did not find evidence that IMRT is more successful than any other kind of radiation therapy in reducing tumors.

Many scientists consider IMRT to be theoretically better able to target cancerous cells while sparing healthy tissues, but more research is needed, the report said. Comparative Effectiveness and Safety of Radiotherapy Treatments for Head and Neck Cancer examines treatment for cancers to the head and neck, including the mouth, larynx, and sinuses. (Tumors in the brain are considered a separate type of cancer and are not discussed in this report.) Nonbrain head and neck cancers account for up to 5 percent of cancers that are diagnosed in the United States, with an estimated 47,560 new cases and 11,260 deaths in 2008. Standard radiation therapy has evolved over the past 20 years and now provides doctors with two- or three-dimensional images that simulate a patient's treatment area on a computer screen. IMRT, which has been implemented over the past 10 years, also employs three-dimensional imaging and further technological and treatment enhancements that tightly control and target the amount of radiation delivered to the target area.

The report also examined the evidence regarding proton beam radiation therapy, a technology that some clinicians believe targets radiation even more precisely than IMRT. However, researchers did not find enough evidence to draw any conclusions regarding the benefits or potential side effects of proton beam therapy, which is more commonly used to treat prostate cancer and pediatric tumors. In an AHRQ Technical Brief published last fall, researchers found limited evidence regarding whether proton beam radiation therapy is safer or more effective than other types of radiation to treat cancer.

The report is part of AHRQ's Effective Health Care Program. AHRQ will also soon publish plain-language summary guides about radiation therapy for head and neck cancer treatment for patients, clinicians, and policymakers. Summary guides on numerous clinical topics such as medicines to reduce the risk of breast cancer and choosing pain medicine for osteoarthritis, as well as other information and background on the Effective Health Care Program, can be found at http://www.effectivehealthcare.ahrq.gov.

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