A new nuclear-arms race is under way - in hospitals.
Medical centers are rushing to turn nuclear particle accelerators, formerly used only for exotic physics research, into the latest weapons against cancer.
Some experts say the push reflects the best and worst of the nation's market-based health-care system, which tends to pursue the latest, most expensive treatments - without much evidence of improved health - even as soaring costs add to the nation's economic burden.
The machines accelerate protons to nearly the speed of light and shoot them into tumors. Scientists say proton beams are more precise than the X-rays now typically used for radiation therapy, meaning fewer side effects from stray radiation and, possibly, a higher cure rate.
But a 222-ton accelerator - and a building the size of a football field with walls up to 18 feet thick to house it - can cost more than $100 million. That makes a proton center, in the words of one equipment vendor, "the world's most expensive and complex medical device."
Until 2000, the United States had only one hospital-based proton therapy center. Now there are five, with more than a dozen others announced. Still more are under consideration.
Some experts see a need for more proton centers. Others contend that an arms-race mentality has taken hold, as medical centers try to be first to take advantage of the prestige - and the profits.
"I'm fascinated and horrified by the way it's developing," said Anthony L. Zietman, a radiation oncologist at Harvard and Massachusetts General Hospital, which operates a proton center.
"This is the dark side of American medicine." Once hospitals have made such a huge investment, experts like Zietman say, doctors will be under pressure to guide patients toward proton therapy when a less costly alternative might suffice.
Similar cost concerns were expressed in the past about other new technology like MRI scanners. While those have become accepted staples of medical practice, there is still concern about their overuse and the impact on medical spending.
Zietman said that while protons were vital in treating certain rare tumors, they were little better than the latest X-ray technology in dealing with prostate cancer, the common disease that many proton centers are counting on for business.
"You can scarcely tell the difference between them except in price," he said. Medicare pays about $50,000 to treat prostate cancer with protons, almost twice as much as with X-rays.
Proponents, however, are adamant that proton centers provide better treatment.
"It all comes down to the physics," said Dr. Jerry D. Slater, the head of radiation medicine at Loma Linda University Medical Center in Southern California.