Anthony L. Zietman, MD
Randomized trials comparing proton beams with standard radiation for the treatment of prostate cancer and other common tumor types are years from completion, but healthcare providers around the nation are betting billions of dollars that the greater accuracy of proton beam therapy will justify the greater costs. The nation’s first proton beam center opened at Loma Linda Medical Center in 1990, but the building boom that has brought the total number of American facilities to 20—most of which can treat more than 100 patients a day—began less than a decade ago, just as some private insurers began citing new research to stop covering proton therapy for prostate cancer treatment.
Despite the financial risk of losing most patients with prostate cancer to conventional radiation therapy, the building boom continues. Another 16 proton beam facilities are either under actual construction or in the advanced stages of planning, according to the National Association for Proton Therapy1
—a fact that observers attribute to everything from the pressure that major cancer centers feel to offer all treatment options to the belief that research will ultimately vindicate a treatment option that irradiates significantly less healthy tissue than any other approach.
Anthony L. Zietman, MD, a noted prostate cancer researcher who is the Shipley Professor of Radiation Oncology at Massachusetts General Hospital, offered a thumbnail perspective on the challenges facing the implementation of the technology.
“Virtually no one was building proton beam facilities when they were seen as primarily offering value for rare pediatric cancers. These had little profit potential because of the slow and complex nature of the treatment,” said Zietman in an interview with OncologyLive
. “Some facilities therefore began recruiting prostate cancer patients, who are substantially more numerous, and quickly realized that prostate cancer was a gold mine. Prostate treatment requires no anesthesia, so they could treat six prostate patients in the time it took to treat one child, but they could still bill the same amount for each treatment.
“But the prostate-cancer model is falling apart. New guidelines that call for less aggressive screening and, in many cases, no immediate treatment when cancer is detected have reduced the number of prostate cancer patients getting any sort of radiation,” Zietman said. “What’s more, Medicare could also follow private insurers and either reduce or eliminate the premium it’s willing to pay for proton beam therapy in prostate cancer payments."
“If we are to support even the current number of facilities going forward, some combination of two things will need to happen. Proton beam therapy will need to demonstrate itself superior to the best photon beam treatment in some common forms of cancer—and there are trials underway that could do that—or centers will have to find a way to survive on standard radiation reimbursement rates,” Zietman noted.
How Proton Therapy Unfolded
The idea of using protons to irradiate tumors dates back to 1946, when the physicist Robert R. Wilson, PhD, suggested it to the research community, which began performing some human experiments with the approach by the 1950s. It took nearly 40 years, however, for the technology to mature enough for that first clinical treatment facility at Loma Linda.
That facility, and those that followed, were both enormous and enormously expensive. Each of those first-generation centers covers nearly as much land as a football field and houses a cyclotron that speeds protons up to more than half the speed of light before using enormous magnets that direct them to gantries, through nozzles that weigh more than 10 tons each and into patients. Construction costs generally ranged from $100 million to $200 million for those 4-gantry facilities, and operating costs added millions more each year.
The advantage to all this expenditure was accuracy. Proton beam therapy allowed for much more granular control over the placement of radiation. It greatly reduced radiation exposure not only for healthy organs surrounding the target in a 2-dimensional plane but also for healthy tissue below the target. Unlike radiation from x-rays, which steadily attenuate after hitting the tumor at full strength, proton beams could be set to penetrate no farther than a target depth.
“When I started in radiation oncology 30 years ago, the things that proton beam therapy can do would be considered absolutely mind-blowing. Standard photon radiation then was effective in treating many tumor types, but the radiation hit so much healthy tissue that its benefits often came at the price of crippling toxicity and a severe risk of secondary tumors,” said Zietman.