Source: MedScape Today
Author: Nick Mulcahy

June 1, 2010 — Intensity-modulated radiation therapy (IMRT) for head and neck cancer leads to fewer cases of xerostomia, but has not yet been proven to be more successful than any other kind of radiation therapy in reducing tumors or improving survival, according to a new comparative-effectiveness review funded by the federal Agency for Healthcare Research and Quality (AHRQ).

The review compares the effectiveness of 4 types of radiotherapy (IMRT, 3DCRT, 2DRT, and proton-beam therapy) in terms of tumor control, overall survival, adverse events, and quality-of-life issues.

Many scientists consider IMRT to be theoretically better able to target cancerous cells while sparing healthy tissue than either 3DCRT or 2DRT, but more research is needed, the authors of the report point out.

The report, entitled Comparative Effectiveness and Safety of Radiotherapy Treatments for Head and Neck Cancer, is authored by the Blue Cross and Blue Shield Association’s Technology Evaluation Center Evidence-Based Practice Center.

The late adverse effect of xerostomia, also known as dry mouth, is less common than in the past because the use of IMRT has allowed radiation oncologists to spare most patients’ salivary glands from radiation as part of treatment planning, an expert recently told Medscape Oncology.

Sparing salivary glands has become standard among clinicians who use IMRT, said Avraham Eisbruch, MD, professor of radiation oncology at the University of Michigan Medical School and Comprehensive Cancer Center in Ann Arbor.

Dr. Eisbruch’s comments came in the context of his study on the use of IMRT to reduce dysphagia in head and neck cancer. However, he also served on the technical expert panel of the new comparative-effectiveness report.

According to the report, it is not known whether IMRT is better or worse at reducing the size of tumors, or whether it improves other outcome measures.

“Inconsistent and nonsignificant results were observed between IMRT and comparators on other adverse events, overall quality of life, tumor control, and survival outcomes. Thus, the evidence is insufficient to support conclusions in these areas,” reads the report.

Overall, the report suffered from a lack of data with which to do comparisons, suggest the authors.

“A small body of randomized, controlled trials is accompanied by a larger body of poor quality observational, nonrandomized studies,” they write about the evidence on the topic.

What About Proton-Beam Therapy?

The main focus of the report was IMRT. An informal survey estimates that 30% to 60% of all patients in the United States are treated with IMRT.

The report authors note that “most of the studies in this review were based on the results of patients treated at academic medical centers.”

Because IMRT is increasingly adopted in community settings, the authors wonder whether results in head and neck cancer will continue to be the same.

“Whether similar results will be achieved as the technology diffuses to less-experienced settings has not been addressed in the comparative studies available for this review,” they write.

The authors sought to examine the evidence regarding proton beam radiation therapy, but there were no head-to-head comparisons to review.

“The strength of evidence is insufficient, as there were no studies comparing proton-beam therapy to any other radiotherapy modality. Therefore, no conclusions can be reached regarding the comparative effectiveness of proton-beam therapy,” write the authors.

Proton-beam radiation therapy is more commonly used to treat prostate cancer and pediatric tumors, the report notes.

In an AHRQ Technical Brief published last fall, researchers found limited evidence with which to determine whether proton-beam radiation therapy is safer or more effective than other types of radiation to treat cancer, according to AHRQ press materials.

The new comparative-effectiveness report is the latest research review from the AHRQ’s Effective Health Care Program, which is an effort to compare alternative treatments for health conditions and to make the findings public, to help doctors, nurses, pharmacists, and others work together with patients to choose the most effective treatments.

The authors are employees of Blue Cross and Blue Shield.