IMRT avoids xerostomia, but effectiveness on controlling cancer unclear

An advanced type of cancer radiation is more successful than traditional radiation in avoiding "dry mouth" when treating head and neck cancers, but 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 HHS' Agency for Healthcare Research and Quality.

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, a potential side effect to radiation when salivary glands are damaged, 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. The comparative effectiveness review, Comparative Effectiveness and Safety of Radiotherapy Treatments for Head and Neck Cancer, was authored by the Blue Cross and Blue Shield (BC/BS) Association, Technology Evaluation Center in Chicago.

"The development of new technologies to treat cancer has been one of the true success stories of American medical research," said AHRQ Director Carolyn M. Clancy, M.D. "This report provides patients and their doctors with more information about these advances, which they can use to make more informed choices about their own treatment."

The report 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.) Non-brain 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.

As with other cancers, head and neck cancer often is treated by radiation, which can damage both cancerous and non-cancerous cells. To limit damage to non-cancerous cells, scientists have sought ways to target high doses of radiation to cancerous cells while sparing healthy ones. This is particularly important with head and neck cancers, because tumors can reside close to vital organs.

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 AHRQ report found that IMRT leads to fewer cases of xerostomia than traditional two-dimensional or three-dimensional radiation therapies, probably because IMRT delivers radiation more precisely. It also found that IMRT improves some aspects of quality of life related to xerostomia. However, the evidence did not conclude that IMRT is better than traditional therapies at reducing the tumors themselves.

In this comparative effectiveness review, researchers 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.  

Comparative Effectiveness and Safety of Radiotherapy Treatments for Head and Neck Cancer is the newest research review from the AHRQ's Effective Health Care Program. The Effective Health Care Program represents the leading federal effort to compare alternative treatments for health conditions and make the findings public, to help doctors, nurses, pharmacists and others work together with patients to choose the most effective treatments.

In conjunction with the new report, AHRQ will soon publish in 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 www.effectivehealthcare.ahrq.gov.

Source:

Agency for Healthcare Research & Quality

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