Unlike typical radiation, proton therapy doesn’t send radiation clear through the body and it keeps the radiation from affecting healthy tissue.
“Because it exits you would have low-dose radiation in the front of the body. But proton, we’re able to tell it to stop when we need it to, so you could see, right past the target it stops completely,” said Rihan Davis, radiation oncology chief dosimetrist at the Laurie Proton Therapy Center, which is part of Robert Wood Johnson University Hospital, an underwriter of NJTV News. The center provides proton therapy in partnership with Rutgers Cancer Institute of New Jersey.
Dr. Rahul Parikh, the center’s medical director, talks about some of the misconceptions with this therapy.
“One of the biggest myths is that perhaps proton therapy is more precise or more accurate. In fact, it’s just as precise as standard radiation, it’s really about the physical properties as you’ve heard, the physical properties of the proton beam,” Parikh said.
He gives the example of a pediatric brain tumor where the tumor is sitting in part of the brain where nearby structures are extremely important – whether it be brain tissue or nerves.
With proton therapy, all the radiation can be delivered to one particular area with little to no dose of radiation elsewhere, sparing healthy and critical tissue.
“When we’re in a tricky location, where surgery can’t be done or can’t be done effectively enough to cure the patient, and we have to deliver high doses of radiation, that go above the tolerability of the structures and nearby organs, that’s when we think about proton therapy,” Parikh said.
The radiation is emitted through the opening of a brass ring — the opening is shaped and custom-made for the patient. An additional piece of the brass helps block out nearby critical structures from receiving radiation.
But this technology is expensive. There are only two proton centers in the state. NJTV News was granted access to the basement of the facility to see the machine behind the therapy.
“To accelerate protons, which is necessary to provide treatment, we start with hydrogen gas. There’s a little bottle, and we pump in just a small amount of hydrogen gas into the center of the accelerator,” said Aaron Devoe, field service engineer for Mevion Medical Systems. “So once the gas is pumped in, we apply a high voltage, and we’re able to isolate the protons. So once the protons are in the center of the accelerator, we induce an electrical field on those protons to start accelerating.”
“So before the protons will exit the machine, they’ll have done about 75,000 revolutions, and they’re going about three cores the speed of light when they exit,” Devoe said.
“That’s where the proton therapy is different it causes direct damage to the DNA of the cancer cell selectively. Whereas standard photons or X-rays use a secondary method. They often cause these free radicals and cause oxidated damage that can secondarily affect the DNA of the cancer cells, and then they try to reproduce and they cannot,” Parikh said.
Parikh says while the cure rate is the same for proton therapy and other forms of radiation, patients treated with proton therapy do have less side effects.
More research is being done to see if there is value in adding proton therapy to treating other cancers like lung, breast and prostate.