The Promise of Proton-Beam Therapy

There's plenty of time for patients to mingle in the waiting room of the $125 million Proton Therapy Center in Houston. In one corner, Alexander Glaros, a 16-year-old with Ewing's sarcoma, plays cards with his mom. In another, a prostate cancer patient in his 60s entertains a toddler who is awaiting treatment for the tumor in her brain. Nearby, a middle-aged woman with lung cancer pages through a newspaper. While they have different types of cancer, all are counting on the same technology, a high-tech radiation treatment called proton beam therapy.

A radiation therapist at M.D. Anderson moves Glaros into position. The rotating device above him, which is connected to a particle accelerator, will fire protons at his tumor.

(Joel Salcido for USN&WR)

Video: Learning About Cancer

In an ideal world, some oncologists say, most cancer patients would get this rare type of treatment, in which doctors use nuclear technology and magnets to fire protons into tumors at about two thirds the speed of light. But just five medical facilities currently offer the therapy, including the one in Houston, which is part of the University of Texas M.D. Anderson Cancer Center. Even with eight more of the expensive facilities planned, there will be nowhere near the number of centers needed to treat every patient who might benefit, proponents of the technology say. ProCure Treatment Centers, a company that partners with hospitals to plan, install, and run the complex facilities, estimates that proton therapy could help a quarter of a million patients. Nationwide, however, only about 6,000 treatment slots are available each year. As a result, doctors face agonizing decisions about whom to treat—and some patients are lucky if they're in a waiting room rather than on a waiting list.

Proton therapy's promise lies in its ability to destroy cancerous cells while sparing healthy cells half a millimeter away, reducing side effects. It also allows doctors to ramp up the radiation dose, theoretically improving cure rates. The precise targeting is possible because the subatomic particles release the bulk of their destructive energy beneath the skin, at the tumor's depth, rather than near the surface, as X-rays do. (Doctors set that depth by controlling the speed at which a proton is blasted at the skin.) And while standard radiation tends to cause damage to healthy tissues on the far side of tumor, protons slow and stop as they release their energy pulse, eliminating a harmful exit dose.

Children are among those who stand to reap the greatest benefits from protons. In pediatric patients, whose bodies are growing, conventional radiation can sow the seeds of secondary cancers and cause a variety of deformities. Proton therapy offers significant benefits for certain adult patients as well: The technology, first tested on patients in the 1950s at experimental nuclear physics labs, is recognized as the most viable way to treat certain rare tumors in sensitive locations, such as the eye, base of the skull, and spinal cord, where even a bit of misplaced radiation can have disastrous results. And current research might even expand its use against various common tumors, including lung and breast cancer.

Heartbreaking choices. Already, the most vexing problem with proton therapy is its limited availability. At Massachusetts General Hospital in Boston, for example, only a fifth of patients who are referred for the treatment end up getting it, and at the proton center at Loma Linda University Medical Center in Southern California, a prostate patient's wait is sometimes measured in months. Choosing who gets treatment and who doesn't can be heartbreaking, says Jay Loeffler, the chief of radiation oncology at Mass General. "You have to pick patients who get the biggest bang for the buck," he says. "You choose a child with a brain tumor you could potentially cure instead of a 50-year-old with metastatic kidney cancer, even though you know you could probably help both."

Competition for precious treatment slots isn't the only obstacle that patients face in getting proton therapy. Many must travel hundreds or thousands of miles and stay near a treatment center for weeks while receiving brief daily doses of radiation. Glaros and his parents, for example, came 781 miles from their home in Overland Park, Kan., for treatment in Houston for the tumor that began as an excruciating pain in his hip and has now spread to his lungs. He isn't supposed to miss even a day of treatment, his mother says, so getting home to apply for his driver's license has morphed into a logistical nightmare.

The dearth of proton facilities is largely due to their high upfront cost. It can easily take $100 million or more to construct the football field-size building needed to house a particle accelerator, the multistory rotating machinery that surrounds each treatment chamber, and heavy concrete shielding walls. The huge price tag means institutions that offer proton beam therapy have often had to go through financial contortions to do so. M.D. Anderson, for example, had originally sought to own its proton center outright and wanted to run it as a nonprofit. When the University of Texas didn't come through with the money, however, planners turned to a consortium of private investors instead.

Such financial realities can put undue pressure on doctors to treat prostate cancer cases, which are relatively simple and quick—and therefore most profitable. Treating a child with cancer, in contrast, can tie up a facility for three or four times as long, adding to the patient bottleneck and slowing an indebted center's ability to repay its loans. "There's definitely pressure from a few of the investors to treat only prostate cancer," acknowledges James Cox, the top radiation oncologist at M.D. Anderson's proton center. Adds Allan Thornton, the medical director at the Midwest Proton Radiotherapy Institute in Bloomington, Ind.: "I've got people breathing down my neck who want to make money on this place." He aims to make prostate cancer about 30 percent of the cases at his institution; Cox, 50 percent at his.

Nevertheless, hospitals say demand for proton beam therapy is ballooning, driven in large part by the huge number of prostate cancer diagnoses—about 186,320 a year—and the favorable impression many prostate patients have of the therapy. Loma Linda, which has been using protons to treat men with prostate cancer since 1991, has published promising results. One study, for example, found major rectal and urinary side effects among less than 1 percent of Loma Linda patients; it didn't specify rates of sexual side effects. Those types of problems are risks associated with other radiation treatments or surgery.

Some men who have received protons at Loma Linda have been so thrilled with their experience that they've become among the technology's biggest boosters, spreading the word through books, chat rooms, support groups—even PowerPoint presentations at churches and clubs. One Loma Linda patient, Robert Marckini, founded what's now a 3,340-member proton therapy support group, the Brotherhood of the Balloon, that has been instrumental in increasing awareness of the technology among prostate patients. "Almost every one of [the members] learned about proton beam therapy from another patient," he says, not from a doctor.

But certain doctors—not to mention the occasional patient who has experienced side effects from proton therapy—wonder whether the high-tech allure of protons hasn't outpaced the science. "Because of Internet buzz, the morbidity associated with proton beam therapy is underappreciated," says Anthony Zietman, a radiation oncologist at Mass General who specializes in prostate cancer. Many of his patients, he says, are surprised to learn that proton beam therapy exposes the bladder and rectum to high doses of radiation and does, in fact, carry a significant risk of causing impotence. Although preliminary research has suggested protons may be superior to conventional radiation for prostate cancer, there's a lack of randomized studies (the type doctors consider most rigorous) comparing the two—and standard radiation techniques are improving all the time.

The lingering questions about prostate cancer are helping to fuel a debate over the location of new proton beam centers and the pace of expansion. Experts who believe prostate cancer should be widely treated estimate there could be a need for scores of new centers. Others contend that five to 10 evenly distributed academic research centers could better serve the rare patients who most need protons—and help determine whether the therapy should be extensively used to treat prostate and other common tumors.

"Prostate mill." In suburban Chicago, the two expansion strategies are at odds. Two centers have been proposed within just a few miles of each other. One would be run by Northern Illinois University as an academic facility; the other by Central DuPage Hospital, which has partnered with ProCure. "To roll out multiple facilities competing against each other is illogical and a waste of resources," says Thornton. An Illinois planning board validated that viewpoint in early April when it denied the latter proposal. Thornton adds that bottom-line considerations could turn a for-profit facility into what he calls a "prostate mill."

Central DuPage plans to appeal. The Chicago area has enough demand, including from some prostate cancer patients, to support as many as six proton centers, says ProCure CEO Hadley Ford. With so many cancer patients lacking access to the technology, he says, the country needs a nationwide network of proton facilities, which is exactly what his company plans to build. And while academic proton centers have been slow to get off the ground, he adds, his company is ready to start building today.

Meanwhile, proton beam technology itself is rapidly advancing. The existing American centers are on the verge of upgrading to what's called intensity modulated proton beam therapy, a beam upgrade that will make it more accurate. Also in the works: drastically cheaper and more compact systems, which are crucial for solving the availability problem. One company, Still River Systems, is working on a system that would fit in one room and cost about $20 million. The device is neither finished nor Food and Drug Administration approved, but eager hospitals are already placing orders.