An analysis of three different types of radiation therapy used to treat nonmetastatic prostate cancer found intensity-modulated radiation therapy (IMRT) may be associated with improved disease control and fewer adverse effects than conformal radiation therapy and proton therapy, according to results of a study presented at a Journal of the American Medical Association (JAMA) media briefing at the National Press Club and published in the April 17 issue of the JAMA.

“Newer radiation treatments—IMRT and proton therapy—hold promise for reducing the side effects of radiation treatment for this disease and improving the cure rates, however, few studies have actually compared outcomes of these different types of radiation,” said Ronald C. Chen, MD, MPH, of the University of North Carolina at Chapel Hill, who presented the findings.

In a nod to comparative effectiveness research in general, the theme of the JAMA issue in which the study was published, the authors wrote that this type of research is needed in localized prostate cancer treatments especially because of the prevalence of the disease and the growth of newer, more expensive treatments that have yet to prove clinical benefit.

In his opening remarks for the briefing, JAMA executive editor, Phil B. Fontanarosa, MD, MBA, said the basic concept of comparative effectiveness research is not new, but this type of research did not receive much funding prior to the American Recovery and Reinvestment Act of 2009, which allocated $1.1 billion to comparative effectiveness research.

“The purpose of comparative effectiveness research is to provide evidence to assist physicians and other clinicians, of course, policymakers and patients to make decisions that will improve healthcare both at the individual level, and the population level,” said Fontanarosa.

The utilization of IMRT exploded over the study period. In 2000, just 0.15 percent of patients were treated with the technique, with the vast majority receiving conformal radiation therapy. By 2008, the proportion receiving IMRT had jumped to 95.9 percent, but Chen explained that this widespread adoption of IMRT was not done on the basis of comparative effectiveness research.

Compared with conformal radiation therapy, IMRT was associated with fewer diagnoses of gastrointestinal adverse effects, hip fractures, and receipt of additional cancer treatments but more erectile dysfunction. Proton therapy was associated with more gastrointestinal adverse effects than IMRT.

Chen and colleagues conducted a population-based study using Surveillance, Epidemiology, and End Results (SEER)-Medicare data from 2000 through 2009 for patients with localized prostate cancer. It compared IMRT, which has been rapidly adopted in recent years and is currently the most commonly used radiation technique, with the older conformal radiation therapy, and also compared proton therapy, which has seen an uptick in use, with IMRT.

Results showed that men treated with IMRT were less likely to receive a diagnosis of gastrointestinal adverse effects than those treated with conformal radiation therapy, with an absolute risk of 13.4 vs. 14.7 cases per 100 person-years. IMRT-treated patients also were less likely to receive a diagnosis of hip fracture (absolute risk of 0.8 vs. 1.0 per 100 person-years), but were more likely to receive a diagnosis of erectile dysfunction (absolute risk of 5.9 vs. 5.3 per 100 person-years). IMRT patients were also 20 percent less likely to receive additional cancer therapy.

In the comparison between IMRT and proton therapy, IMRT patients had a 34 percent lower risk of gastrointestinal adverse effects and there were no significant difference in the rates of other adverse effects or additional therapies received.

"Proton therapy is a high-profile, high-cost prostate cancer treatment. Since 2007, multiple proton facilities have been built, and direct-to-consumer advertising is likely to lead to a substantial increase in use," wrote the authors. "Overall, our results do not clearly demonstrate a clinical benefit to support the recent increase in proton therapy use for prostate cancer."

Chen said he believed patients had a part to play in the decision of which treatment to receive based on their evaluation of the differences in risks between the treatments, though he said choice might be limited due to the relatively small number of proton therapy sites. Despite proton therapy’s growing use, there are many more IMRT providers around the country.