In proton therapy, the medical team directs a beam of sub-atomic protons at the patient's tumor site. The protons are able to accurately target and kill tumors—both near the surface and seated deep within the human body—while minimizing damage to surrounding tissues and organs. This is a particular problem for tumors around optical nerves, the spinal cord, the head and neck, the prostate, and the central nervous system, areas where conventional radiation would damage the surrounding tissue.
Proton therapy utilizes a more controlled dose of radiation than other radiation treatments, thereby reducing severe side effects to healthy tissue. But building cancer treatment centers that can handle the process that unlocks the potential of protons comes with its own side effects for Building Teams.
“You essentially have to shield the area from escaping neutrons, the reactionary particles in the neutron bomb,” says Ed Tsoi, FAIA, principal of design firm Tsoi/Kobus & Associates, Cambridge, Mass., which has designed four proton therapy cancer centers: the University of Texas M. D. Anderson Cancer Center, Houston; the University of Pennsylvania Health System Roberts Proton Therapy Center, Philadelphia; the Massachusetts General Hospital Cancer Center, Boston; and the University of Florida's Shands Jacksonville Medical Center.
Keeping the neutrons from escaping
The initial problem of creating atomic reactions is keeping dangerous radiation, such as neutrons, which are created and deflected when a proton stream collides with a tumor or wall, from escaping the treatment space. This often requires designing walls that are 6-10 feet thick for treatment rooms, and at least 10-foot-thick ceilings.
“The equipment costs more than the building itself,” says Tsoi. “So it's necessary to design the building in the most cost-effective way possible.” One way is to use the earth itself as the radiation barrier and build the treatment rooms below ground.
In urban facilities such as the Roberts Proton Therapy Center, where below-grade construction would be hampered by the building above, it was necessary to design thick concrete planks that interlock like Lincoln Logs, to allow part of the ceiling to be removed if major pieces of equipment need to be maintained or replaced.
For the M. D. Anderson Cancer Center, which opened last summer, the program includes four proton therapy rooms, an imaging center, and experimental areas for research. The target is to treat 3,000 patients a year, among them the 40% of U.S. males who will have prostate cancer at some time in their lives, according to the American Cancer Society.
The institutions and business partners who are planning tomorrow's proton therapy centers have become more concerned about how many patients can be treated per day and per year. “The cost to construction these facilities is obviously very high so we are focused on how to get higher utilization of equipment,” Tsoi said. If set-up for each patient is reduced and the staff is available to treat patients beyond a normal 8-hour day, there is an improved return on investment. Once the equipment is in place, the challenge is to find the means to offer this treatment to as wide a variety of patients as possible.”
Typical treatments take 30-45 minutes and are painless. While results can vary significantly based on the types of patients seen, the kinds of tumors treated, and the stage of the disease, proton therapy has yielded very high success rates for well-defined tumors—in the upper 90% range.
“The push from the physicians, physicists, and businesspeople that invest in these facilities is to find a way to apply this protocol to new sites such as lung and breast cancer,” says Tsoi. “We're seeing research into new cancer sites at places like MGH, M. D. Anderson, University of Floriad and Loma Linda as well as overseas in Europe and Asia.”