The Proton Treatment Center at Loma Linda University Medical Center in California, which opened in 1990, was the world’s first hospital-based proton treatment center. Since that time, proton therapy centers have opened at Massachusetts General Hospital, Indiana University in Bloomington, the University of Texas M.D. Anderson Cancer Center, and Shands Medical Center at the University of Florida Proton Therapy Institute. New centers are under construction in Oklahoma City and at the University of Pennsylvania Health System (UPHS) in Philadelphia, which will be the largest proton center yet.

“There really are no defined standards on whether it is best to integrate a proton therapy center within a larger building versus developing a completely free-standing facility,” says Edward Tsoi, senior principal of Tsoi/Kobus & Associates in Cambridge, Mass. “There are advantages and disadvantages to consider with each configuration based on the availability of space, whether proton therapy can be combined with a comprehensive radiation oncology program, and the institute’s overall vision.”

Tsoi is leading design efforts at UPHS, the ProCure Treatment Center at Central DuPage Hospital, and the Oklahoma ProCure Treatment Center, and has contributed to the design of proton centers at Mass General, M.D. Anderson, and the University of Florida.

What is Proton Therapy?

Protons (charged particles) are hydrogen atoms whose electrons have been removed. Proton beam radiotherapy uses an accelerator (cyclotron or synchrotron) to energize protons. Protons are extracted from the accelerator and directed with magnetic fields that guide the proton beam to treatment rooms and ultimately through equipment that targets specific tumors within patients.

Protons differ from traditional x-ray treatment because they deposit the highest dose of energy when they stop inside the body, giving radiation oncologists greater control in directing and depositing high levels of destructive energies at the tumor. Because a radiation oncologist has the advantage of precisely targeting the tumor, the patient receives the strongest radiation treatment possible with minimum damage to surrounding organs or tissue.

Since tumors can have very irregular shapes, every patient’s tumor shape, size, and location are unique. Proton therapy allows technicians to define the proton beam so that it is customized for each tumor while minimizing the dose to healthy organs.  Proton therapy is considered the latest in three-dimensional forms of radiation therapy.

Integration Within a Larger Facility

Delivery of the cyclotron at UPHS is scheduled for late this year, and the center expects to treat its first patient with proton therapy in 2009. The new center will include five proton treatment rooms: four gantry-style rooms and one fixed-beam room, all located on the same floor as the hospital’s radiology oncology department. It also plans to operate under a joint arrangement with the adjacent Children’s Hospital of Philadelphia to include proton therapy for pediatric patients.

“An integrated proton center will allow all radiology treatments to take place under one roof, which we feel is important for multidisciplinary care,” says James M. Metz, M.D., assistant professor and chief of clinical operations for the department of radiation oncology at UPHS. “This will let us locate researchers and clinicians in the same building and will contribute to our overall focus as an academic medical center.”

Integration within a larger facility also offers the advantage of less equipment redundancy if patients require additional imaging needs, including MRI testing, x-rays, or CT scanning.

“Radiation oncologists often suggest that proton therapy be combined with other conventional radiation treatments to reinforce the cure,” says Metz. “Having all of our radiology staff, including the proton therapy specialists, centrally located will be much more convenient for the patient and for our staff.”

According to Tsoi, the main challenge of integrating a proton center into a larger facility relates to heavy shielding requirements that are necessary to protect against the escape of stray neutrons.

“Stray neutrons can be quite damaging to human cells so they need to be kept tightly controlled within designated areas in the proton facility,” says Tsoi. “The most cost-effective way to do this is to build the proton center in the lower levels of the building or at least partially below-grade so that the surrounding soil acts as shielding.”

He adds that shielding for above-grade facilities can also be accomplished with very thick concrete walls ranging in width from six to 12 feet, which typically increases project costs.

“The proton center at the University of Florida is above-grade because it would have been more expensive to build below ground due to Florida’s high water table,” says Tsoi. “In that case, it was less expensive to add more concrete shielding at the street level.”

Freestanding Proton Centers

In contrast to proton centers that are integrated into larger facilities, freestanding proton centers are able to establish a separate building identity. When proton centers are freestanding, the design is not bound by existing design parameters and structural requirements of the larger facility, which may be on top of the proton facility.

However, Tsoi explains that patients can also be inconvenienced by freestanding proton centers if those facilities do not offer other forms of radiation treatments or house other specialists related to the treatment.

He adds that both freestanding and integrated proton therapy centers share similar design challenges involved in incorporating the large, very heavy equipment used to deliver protons.

“The layout of treatment rooms is defined primarily by the equipment because of its size and because proton-beam delivery requires extreme precision,” says Tsoi.  “Size is especially critical when adding a gantry-style treatment room, which requires three stories in height.”

Gantries are 90-ton rotational machines with 35-ft diameter wheels that allow the beam to rotate a full 360 degrees so that the proton beam can be aimed at the tumor from various directions. The lowest level, below the patient treatment room, contains the gantry supporting structure. When the patient enters the treatment room, the only visible part of the gantry is inside this very large cylinder.

The patient room itself requires another two stories so that the proton beam can fully rotate around the patient. Patients lie on a robotic bed that can be adjusted for precise alignment of the proton beam. A nozzle is used to direct the beam precisely to where it is needed.

Some tumors, such as eye tumors, can be treated by having the patient site in a chair. The beam does not move, but rather the patient is positioned to receive a dose of protons from a “fixed beam.” The rooms are one-story tall since no gantry is required.

Tsoi also points to ongoing equipment maintenance as another challenge of integrating a proton center within a larger facility.

“Since gantry wheels are so large and heavy, it will be extremely difficult to replace this type of equipment in the future, but we have to make provisions for this potential maintenance within the building design.”

He explains that this can be done by designing a hatch in either the side walls or the roof of the proton treatment room. The hatch should be big enough to allow a crane to remove or replace the segments of the gantry and other equipment if necessary.

At UPHS, the hatches are located in the walls of the proton treatment rooms and are made up of very large precast concrete panels that can be removed.

Determining Facility Size

“In our analysis, one accelerator should support no more than four or five treatment rooms,” says Metz. “We plan to dedicate one room specifically to pediatrics. It takes much longer to treat each pediatric patient, so for us it makes sense to have five rooms.”

Tsoi agrees that five is a comfortable maximum number of treatment rooms that should be served by one accelerator.

“In order for the proton beam to adequately serve all of the treatment rooms, the rooms must be lined up in a row like train cars along one long corridor,” says Tsoi. “Beyond five rooms, the corridor length of the proton’s path gets too long to control the precision and efficiency of the proton beam.”

After leaving the accelerator, the protons move through a beam transport system that includes a vacuum tube in the corridor wall leading to each treatment room. A series of steering and focusing magnets guide the protons through the vacuum tube into a nozzle that is used to treat the patients.

Controlling Facility Cost

According to Tsoi, proton centers can range in today’s costs from $600 to $800 per square foot of building area, depending on the number of treatment rooms and whether the facility is above- or below-grade.

The projected total cost for the new proton center underway at UPHS is approximately $150 million, with one-third of that allocated for the purchase of the cyclotron and other specialized equipment, one-third for the building, and one-third for other soft costs.

“Part of our project costs also included working with our local electrical company to build a new substation since the electrical infrastructure needed to be upgraded to support the cyclotron,” says Kevin Mahoney, senior vice president and chief administrative officer at UPHS.

He adds that in order to help control project costs, UPHS worked with a physicist from the University and an outside consultant to discuss ways to reduce shielding costs.

“To ensure that we paid the best equipment prices we held a competitive bid process between the two leading accelerator manufacturers, Ionic Beam Applications (IBA) of Belgium and Hitachi of Japan, and ultimately selected IBA,” says Mahoney. “As more equipment providers enter the accelerator market, hopefully lower prices will result from increased competition within this arena.”

He adds that costs can also be controlled by using a combination of fixed beam rooms with gantry rooms since fixed beam rooms offer higher patient throughput, and by studying ways to reduce the time interval involved in switching the beam between patient rooms.

To increase patient throughput, physicians and researchers at UPHS are working together to develop Multileaf Collimators (MLC) to minimize support products such as apertures that are required in the treatment rooms. This will allow patients to be treated without technologists entering the rooms between fields.

“Since proton therapy is considered an emerging treatment, reimbursement rates from insurance providers in the U.S. are only slightly higher than conventional radiation therapy,” says Mahoney. “This does complicate the business model for proton therapy centers but we are still predicting that it will take less than two years for our center to recover our initial investment.”

It is projected that UPHS will treat 3,000 patients a year, including several hundred children through its partnership with Children’s Hospital of Philadephia.

According to Metz these numbers are based on the proton center operating at full-capacity during a 16-hour day, treating up to 40 patients per treatment room. During an 8-hour day, approximately 20 patients can be seen per treatment room.

“Patient throughput in proton centers typically varies slightly based on the style of the treatment room,” says Tsoi. “It takes longer to set up a patient in gantry-style rooms since it is important to properly align the patient within the room and on the table.”

He adds that patient set-up is less complicated in fixed-beam rooms where patients sit upright in a chair and are treated by a stationary beam.  This set-up is used most often for irradiating eye tumors or for concentrating on tumors in the head and neck.

To date, the proton treatment center at the University of Indiana is the only center that includes an inclined-beam room, which can be moved about 60 degrees.

“As proton therapy continues to mature as a science, there is no doubt that new sources of capital will continue to emerge to support this field,” says Mahoney.  “Because of its potential as a superior cancer treatment, proton therapy often attracts large donations from individuals, which is what happened at our facility when the Roberts family of Philadelphia came forward as a major donor.”

He predicts that proton therapy will also continue to attract more government grants and funding from commercial sources that are interested in helping to advance proton therapy as a science.

By Amy Cammell