Alice Fisk's fainting spell during a trip to Paris in 2000 uncovered a tumor on the lining of her brain, leaving the 56-year-old from Wilmington, Del., with a terrifying treatment - brain surgery.
Fisk decided to hold off on the operation until the tumor's growth forced the issue. When that point arrived in August 2005, Fisk's Harvard University neurosurgeon gave her a new option - proton beam therapy, a type of radiation offered at only a few hospitals in the country.
So she traveled to Boston for six weeks of treatment that she says was painless and left her feeling like her old self.
"What is amazing about it is they measure the tumor so closely that only the tumor itself receives radiation," says Fisk, now 62.
In a couple of years, people like Fisk won't have to travel so far. The University of Pennsylvania is building a $144 million proton therapy center on the old Philadelphia Civic Center site, scheduled to open in 2009. It would be one of only seven in the nation that use the tiny particles to destroy tumors.
Believers in the novel approach say the proton beam delivers the radiation so precisely that the therapy kills tumor cells while largely sparing nearby tissue. They say that's especially important with children - to avoid long-term side effects - and in adults with tumors near vital organs such as the brain.
"We feel we are going to be able to treat tumors in very, very difficult-to-reach positions," says Stephen M. Hahn, head of radiation oncology at the Penn health system.
The precision of proton therapy comes from the physical properties of the particles. The radiation dose deposited by a proton beam peaks when it reaches the tumor, increasing three to four times in intensity. After that point, known as the Bragg peak, the energy of the particles quickly drops to zero, limiting collateral damage.
In Penn's proton program, a beam will be created using a 220-ton machine called a cyclotron. The massive machine, which consists largely of steel and electrical coils, generates a magnetic field that causes the particles to move in a circle. During each cycle, the protons pass by a radiofrequency system that boosts their speed.
The charged particles are then sent down a long pipe, or tube, with branches leading to each treatment area. There, it is fed through a mechanism that varies the beam's energy, extending the Bragg peak to conform to the three-dimensional shape of a tumor.
