Proton therapy will revolutionize treatment and research

by Tim Bonfield

Proton Therapy Center construction site.

Most of the massive structure required to support the machinery within the Proton Therapy Center will never be seen by the patients treated there. More than 31,000 yards of concrete and 600 miles of rebar will be almost entirely underground once the center opens in winter 2016-17.

Enough concrete to pave a sidewalk from Cincinnati to Louisville. A machine that weighs as much as three passenger jetliners, and accelerates subatomic particles to over 100,000 miles per second. An investment exceeding $120 million.

All of it to provide the best radiotherapy treatment available for children and young adults with brain tumors, lymphoma, sarcomas and other cancers.

These are just some elements of the new Proton Therapy Center under construction at Cincinnati Children’s Liberty Campus. The facility reflects the latest evolution in pediatric cancer care, and when it opens in winter 2016-17, it will be one of only two such centers in the country owned by a pediatric medical center.

“For the rising numbers of children who survive their cancers, this form of therapy will help them live much healthier lives for their next 50 years,” says John Breneman, MD, radiation oncology medical director of the new center. “We expect proton therapy to become a new option for previously untreatable tumors, and to sharply reduce the long-term side effects that often occur with conventional radiotherapy.”

For many children with cancer, proton therapy is the most precise and advanced forms of radiation treatment available, according to the American Brain Tumor Association. It can significantly reduce the risks of learning disabilities, heart damage and secondary cancers that can be triggered years later by exposure to conventional radiotherapy.

The Proton Therapy Center will replace conventional radiation treatments for more than 80 percent of children with cancer treated here, says Breneman, one of the nation’s leaders in pediatric radiation therapy. This approach will be especially valuable for treating medulloblastomas and other brain tumors that can be difficult to treat with surgery and chemotherapy. It will also avoid damaging the heart, blood vessels and lungs when treating lymphomas in the chest.

Although more than 200 medical centers in North America provide pediatric cancer care, to date, only 13 facilities provide proton therapy. The Cincinnati facility will serve families from Cincinnati and the surrounding region as well as patients referred here from other parts of the U.S. and the world.

HOW PROTON THERAPY WORKS

Traditional radiotherapy delivers beams of X-ray energy (photons) that kill cancer cells, but also strike healthy tissues on the way into the tumor and on the way out, significantly limiting the safe maximum intensity of the treatment.

Proton therapy involves pencil-thin beams of particles (protons) that are generated by accelerating hydrogen ions in a cyclotron to two-thirds the speed of light. Accurately aimed particles stop inside the tumor, where they release all their energy, a phenomenon known as the Bragg peak. This virtually eliminates exit damage, which means proton beams can carry higher doses of cancer-killing energy and can target tumors located closer to critical structures.

Patients typically receive proton therapy five times a week for two to eight weeks. Using varying intensities of the proton beam, therapists “airbrush” tumors layer by layer, constantly adjusting to the tumor’s irregular shape. The most challenging aspect is to precisely aim the particles as tumors move inside growing, breathing, restless patients. Much of the expense involved in building the Proton Therapy Center goes into the massive, computer-controlled gantries, the equipment that aims the particles as they rotate around the patient. Each gantry is about the size of a house.

“You want all of the radiation on the tumor, and if possible, none of it reaching beyond the tumor,” says Breneman, who also serves as vice-chair of radiation oncology at University of Cincinnati (UC) Health. “Proton therapy comes much closer than conventional radiotherapy to achieving this.”

The Proton Therapy Center’s massive gantries will aim proton beams at tumors.

In the space currently filled with scaffolding (top), the Proton Therapy Center’s massive gantries will aim proton beams at tumors. The protons will be generated by a 90-ton cyclotron (middle), then accelerated along an underground track (bottom).

 CENTER TO PLAY LEADING ROLE IN RESEARCH

Research will play an integral role in the new facility. One of the gantries will be dedicated exclusively to research and development – making it the only fully dedicated proton research gantry in the world, says John Perentesis, MD, Executive Co-Director of the Cancer and Blood Diseases Institute. This gives a cross-campus team of scientists from Cincinnati Children’s and five colleges of the University of Cincinnati unprecedented access to an emerging technology.

Experts in cancer biology, genomics, particle physics, and engineering have already begun studying ways to refine and expand the use of proton therapy. Projects include studying the biological effects of proton radiation across differing types of tumors and tissues, cancer stem cell research, and developing new therapies. Other projects will evaluate and sharpen imaging technology and computer tracking systems.  Longer-term clinical studies will track outcomes and identify ideal dose levels for various cancers and age ranges, Perentesis says.

The Proton Therapy Center also will anchor a new inpatient and outpatient oncology treatment center at the Liberty Campus, developed in conjunction with the UC College of Design, Art, Architecture and Planning and its Live Well Collaborative.

“Our objective is to use 21st century technology to transform and extend the compassionate and supportive environment that families and patients already experience when receiving cancer care here, from initial diagnosis all the way through to survivorship,” Perentesis says.

 10 YEARS IN THE MAKING

Planning for the Proton Therapy Center reaches back a decade and will intensify in the coming months. As the project moves into final construction, Abram Gordon, the Center’s executive director, will manage a flurry of details – including the mid-2015 shipment of a 90-ton cyclotron from Germany to Cincinnati.

The cyclotron is so large it requires a special, multi-axle trailer to move. Roads will be closed at certain points along the route. A powerful crane will be needed to hoist the equipment into place once it arrives. The trip will take several weeks.

It will take another year to 18 months to complete the assembly, calibrate the device and obtain required inspections and approvals.

“It is a complex and expensive project,” Gordon says. “Not every medical center has the resources to build something like this. But once it’s ready, it will significantly improve the outcome for children with cancer.”


Protons versus x-rays.

Proton beams stop within the tumor rather than passing through the body, which limits radiation exposure of surrounding tissue.

Proton Therapy Center at a Glance

  • Treatment to begin in winter 2016-17
  • Treatment indicated for up to 85 percent of pediatric tumors
  • Location: Cincinnati Children’s Liberty Campus
  • Cost: $120 million
  • Features: Varian ProBeam® Proton Therapy system, including two clinical gantries and one gantry dedicated to research. The building includes space to add another gantry.
  • Cyclotron, the heart of the system, weighs 90 tons, equivalent to three empty 737 jetliners
  • Housing the particle accelerator track and gantries requires 31,000 yards of concrete, enough to pave a 120-mile sidewalk from the therapy center to Louisville, Ky.
  • Materials include 155 miles of wiring and 600 miles of rebar.