First Compact Proton Therapy Machine For Cancer Treatment Enters Development

Proton therapy is considered the most advanced form of radiation therapy available, but size and cost have limited the technology’s use to only six cancer centers nationwide.

The result of defense-related research, the compact system was developed by scientists at Lawrence Livermore National Laboratory in a project jointly funded by the Laboratory and UC Davis Cancer Center.

In the new technology transfer pact, Lawrence Livermore National Laboratory has licensed the technology to TomoTherapy Incorporated (NASDAQ: TTPY) of Madison, Wis., through an agreement with the Regents of the University of California.

TomoTherapy will fund development of the first clinical prototype, which will be tested on patients at UC Davis Cancer Center. If clinical testing is successful, TomoTherapy will bring the machines to market.

“We are very pleased that the basic research of our department’s defense scientists may also serve the nation by helping to make proton therapy more available to cancer patients,” said Raymond L. Orbach, the U.S. Department of Energy’s Under Secretary for Science.

“This technology has grown out of work to develop compact, high-current accelerators as flash X-ray radiography sources for nuclear weapons stockpile stewardship,” said George Caporaso, the lead scientist on the project at Lawrence Livermore. “We are excited about applying this new technology to the field of cancer treatment, to make proton therapy widely available as a treatment option.”

"We have taken proton therapy and achieved major advances toward what we were told was impossible – to scale it down to a size and price that will bring it in reach of every major cancer center,” said Ralph deVere White, director of UC Davis Cancer Center and associate dean for cancer programs. “Our research partnership with Lawrence Livermore National Laboratory has fulfilled the mission for which it was created: to deliver translational research in order to advance health care.”

Conventional radiation therapy kills cancer cells using high-energy X-rays. These X-rays deliver energy to all the tissues they travel through, from the point they enter the body, until they leave it. Doctors therefore have to limit the dose delivered to the tumor to minimize damage to surrounding healthy tissue.

Unlike high-energy X-rays, proton beams deposit almost all of their energy on their target, with a low amount of radiation deposited in tissues from the surface of the skin to the front of tumor, and almost no “exit dose” beyond the tumor. This property enables doctors to hit tumors with higher, potentially more effective radiation doses than is possible with gamma radiation.

“Until proton therapy is more common and we can do large comparative studies, we can’t say with specificity what the impact will be on survival and other treatment outcomes,” said deVere White, a urologic oncologist. “However, we expect that outcomes will be significantly better. As with other advances we have seen in cancer, this will re-set the norm of what constitutes best therapy.”

One of the largest studies of proton therapy, published in the June 1, 2004, issue of the International Journal of Radiation and Oncology, looked at 1,255 men who were treated for localized prostate cancer during the 1990s at the Loma Linda University Medical Center’s Proton Treatment Center in Loma Linda, Calif. The study concluded that proton therapy yielded disease-free survival rates comparable to those of surgery or conventional radiation, but with minimal to no side effects, such as incontinence and impotence.

Charged protons were first used in the successful treatment of human cancer in experiments at the Berkeley Radiation Laboratory more than 50 years ago. But because the machines can cost more than $100 million to build and can require 90,000 square feet to house, today only six centers in the United States offer proton treatment: Loma Linda, Massachusetts General Hospital’s Francis H. Burr Proton Therapy Center in Boston, M.D. Anderson Cancer Center’s Proton Therapy Center in Houston, Midwest Proton Radiotherapy Institute in Bloomington, Ind., and the University of Florida Proton Therapy Institute in Jacksonville, Fla. In addition, UC Davis Cancer Center offers proton therapy for ocular melanoma only.

Worldwide, there are 25 proton therapy centers in operation. Together, they have treated an estimated 40,000 patients.

The compact system is expected to fit in standard radiation treatment suites and to cost less than $20 million. The compact system will be mounted on a gantry that rotates about the patient.

Caporaso’s team overcame the size obstacle by using dielectric wall accelerator technology developed through defense research. The Livermore scientists have demonstrated in principle that this technology will enable proton particles to be accelerated to an energy of at least 200 million electron volts within a light-weight, novel, insulator-based structure about 6.5 feet long. It also won’t use any bending magnets, and will be able to change the protons’ energy and intensity between each burst that occurs many times per second.

Currently available proton therapy machines use cyclotrons or synchrotrons nearly 10 feet in diameter and weighing up to several hundred tons. This equipment includes the enormous gantry and bending magnets necessary to focus and direct the beams onto patients.

In addition to overcoming size and cost obstacles, the compact system will improve on existing full-scale systems by including the capability to vary the energy, intensity and “spot” size of the proton beam. Radiation will be produced in rapid pulses, creating small “spots” of dose throughout the tumor. Currently only one proton facility in the world, the Paul Scherrer Institute in Switzerland, is able to deliver this intensity-modulated proton therapy (IMPT). IMPT is generally considered the best way to destroy tumors while minimizing damage to surrounding healthy tissue.

TomoTherapy Incorporated was established to commercialize another radiation therapy advance developed by university researchers, the Hi-Art® treatment system. That system, which marries a CT scanner to a state-of-the-art linear accelerator, was developed by Thomas “Rock” Mackie and Paul Reckwerdt at the University of Wisconsin.

“We look forward to partnering with Lawrence Livermore to commercialize this technology for such a great cause,” said Reckwerdt, co-founder with Mackie of the company. “Proton therapy has recognized advantages in the treatment of many cancer sufferers and we hope to be able to make it widely available.”