Researchers accelerate proton cancer treatment

Technology being developed at Lawrence Livermore lab could soon make more precise radiation therapy widely available to cancer patients by making the specialized machines more compact.

Artist's rendition of a compact proton-therapy system.
Artist's rendition of a compact proton therapy system. Lawrence Livermore National Laboratory

For bone cancer patient Nicole McLaughlin to get proton-beam radiation therapy--a treatment to which she owes her life--it took traveling across the country to what then, in 1999, was the only facility providing such technology.

But new research being developed at Lawrence Livermore National Laboratory, which could reduce the size of proton accelerator machines from that of a football field to that of a traditional X-ray machine, could soon make proton therapy more easily accessible to all.

Better-known X-ray radiation goes all the way through the body and can cause healthy cell death, which could be potentially catastrophic depending on where the tumor is located, like near the spinal cord, neck, or in McLaughlin's case, the sacrum. Proton therapy is different because the proton beam can be controlled to go only as deep as the tumor, precisely targeting it without damaging the surrounding healthy cells and, therefore, causing fewer side effects.

After eight months of intensive chemotherapy, McLaughlin's parents sent her MRIs to some of the best oncologists around the U.S. They were hoping for an exception to the same answer they had been getting--without surgically removing her sacrum, she would die of osteosarcoma bone cancer. But every doctor agreed surgery was the only option.

Only 18 years old at the time, removing McLaughlin's sacrum would have left her permanently in a wheelchair and incontinent.

"It's sad what we were thinking of doing," says McLaughlin's mother, Pat McLaughlin of Hollywood, Fla., remembering that they had almost agreed to the surgery.

"It's sad what we were thinking of doing."
--Pat McLaughlin, mother of cancer patient

Finally, after imploring a radiation therapist in Gainesville, Fla., for some sort of advanced radiation treatment, the therapist mentioned hearing about proton-beam therapy, which at the time was only available in Loma Linda, Calif.

"We sent her MRIs and were on the next plane," says McLaughlin's mom.

McLaughlin's proton treatment didn't physically hurt her at all; she was treated 10 minutes a day, five days a week for two and a half months without any side effects. Not only did McLaughlin beat cancer, but she avoided surgery and the painful and potentially very serious side effects of traditional X-ray radiation therapy.

View through the port of a proton source test chamber.
View through the port of a proton source test chamber. Jacqueline McBride/Lawrence Livermore National Laboratory

Proton-beam therapy has been around for decades. In the late 1980s, Loma Linda University Medical Center installed a proton accelerator and became the first hospital in the world to give proton treatment. But even though proton therapy is not new, it's still not widely known.

With only six proton centers in the U.S. and 25 to 30 centers in the world, most doctors don't readily recommend the treatment. In addition to their size, proton accelerator machines are up to three stories high and can cost $100 million to build.

Proton therapy for all
But Lawrence Livermore's research, spearheaded by radiation therapy company TomoTherapy, could soon change this. For the past five years, scientists have been working on a compact proton-beam machine called a dielectric wall accelerator (DWA), which works similarly to the giant machine in Loma Linda but is a fifth the cost and only the size of a traditional X-ray machine.

Originally, George Caporaso, the beam research program leader at Lawrence Livermore, was working to develop compact flash X-ray accelerators for nuclear weapons stockpile stewardship. While doing this research, another scientist asked Caporaso if he could apply this same technology to proton accelerators for medical purposes. Caporaso hadn't heard of proton therapy, but looked into it and decided that, "it looked very hard but feasible."

When he began research, there were only three proton centers in the U.S., and all used one of the two types of proton beams, cyclotron or synchrotron. The cyclotron is the same kind of machine used to treat McLaughlin's tumor--it was originally developed for physics research to study the nature of matter but was later adapted for medical purposes. Both the cyclotron and synchrotron add energy by spinning particles in a circle.

"The DWA is entirely different," says Shawn Guse, the CEO of the Compact Particle Acceleration Corporation, which was founded by TomoTherapy specifically to work on the compact proton-beam project with Lawrence Livermore. "It is a completely different way to accelerate a particle."

"It looked very hard but feasible."
--George Caporaso, beam research program leader at Lawrence Livermore Lab

Only a 5- to 6-foot-long tube, the DWA applies energy to a particle in a straight line. As the particles move down the tube, the energy of the protons can be controlled very precisely and in a targeted manner. "It's like working with a 2-millimeter-wide scalpel compared to a 10-millimeter scalpel to get at smaller areas with damage," says Guse.

Caporaso describes the tube as looking like a "multilayer sandwich," with thin sheets, less than one millimeter thick, bonded together in alternate layers of conductor and insulator. These scientists are designing and making every component used in the compact machine and, Caporaso says, they are "pushing the state of the art in virtually everything."

Lawrence Livermore Lab electrical engineer Jim Watson tests the compact proton source.
Lawrence Livermore Lab electrical engineer Jim Watson tests the compact proton source. Jacqueline McBride/Lawrence Livermore National Laboratory

The DWA will be more precise than the cyclotron and synchrotron because doctors will be able to administer the therapy more dynamically. Both the patient and the beam will be moving at the same time, resulting in better accuracy and speed. This type of movement is possible because of perhaps the most revolutionary aspect of the DWA--its size.

The entire system will be able to fit in the same size treatment vault as a traditional X-ray room, which means that, in theory, proton therapy can be as widespread as X-rays, available in any hospital and any town. Having smaller machines and less infrastructure means lower costs, all of which contribute to the scientists' goal of making proton therapy as accessible as X-ray therapy.

"Right now, there is a waiting list at Loma Linda," says Caporaso. "There is a big demand for this type of treatment and it has the potential to be widely available if we're successful."

The prototype won't be done for at least three more years; however, TomoTherapy and Lawrence Livermore have confirmed that the proof of concept has been determined.

This means the possibility for compact proton-beam therapy is imminent and hopefully will make it much easier for people like McLaughlin, now 28, to have the same results in finding a cure for cancer.

That should only fuel her parents' continued effort to get the word out about proton treatment. For without it, mother Pat McLaughlin adds, her daughter "probably wouldn't be here."

"There's no push to recommend the treatment and we think that's sad."

About the author

Dara Kerr, a freelance journalist based in the Bay Area, is fascinated by robots, supercomputers and Internet memes. When not writing about technology and modernity, she likes to travel to far-off countries.

 

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