But what about proton beam therapy, which costs even more than IMRT - but which did no better in the Chen study?

“This is not to say that at the end of the day, proton beam radiation is not right for prostate cancer,” Potters says. “It’s just we need to do additional study of it. And given the rate of construction of proton machines on a national level, the data should be more forthcoming to show whether it’s worth the expense for prostate cancer.”

Chen notes that doctors switched from 3D conformational therapy to IMRT even before there was hard data to show it might be better. As more and more medical centers build proton beam facilities, he suggests that doctors might again switch to the next new thing.

“We are saying, ‘Wait a minute, let’s compare outcomes before we jump to a new therapy,’” Chen says. “I don’t think this study prevents a prostate cancer patient from choosing proton beam therapy. But it does tell him to ask his doctor about showing him data on whether protons are better.”

Much of the data that is available contradicts the Chen study, says Nancy Mendenhall, MD, medical director of the University of Florida Proton Therapy Institute and associate chair of the university’s department of radiation oncology.

Mendenhall says the Chen study fails to collect important data, such as the doses radiation patients received, exactly how well their tumors responded to treatment, and exactly which toxicities the patients suffered.

She says that studies from proton therapy centers find far lower rates of side effects than the Chen study did.

“There is discordance between what is in the published proton therapy medical literature and this study, for which there is no explanation,” Mendenhall says. “There is so much we don’t understand here. ... We don’t have the data we need for disease control and morbidity.”

Not included in the Chen study was another effective form of radiation therapy for prostate cancer: brachytherapy, the implantation of radioactive seeds.

Potters recommends brachytherapy to his patients. “From a comparative perspective, this remains one of the mainstay options for prostate cancer,” he says.

But Chen says brachytherapy is appropriate only for patients with early prostate cancer.

“So brachytherapy is not a fair comparison with the others because it can only be given to a limited number of patients,” he says.

The Chen study appears in the April 18 issue of the Journal of the American Medical Association.

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By Daniel J. DeNoon