St. Jude Proton Therapy: Think Positive

St. Jude opens the first proton therapy center just for children.

The power of protons

Just as a spider shoots a gossamer line with incredible accuracy, the St. Jude proton therapy equipment propelled sub-atomic particles into Kennedy’s tumor with phenomenal precision. This level of accuracy also minimized damage to her healthy tissues and organs.

Located 60 feet underground, the new Proton Therapy Center harnesses the power of protons to treat brain tumors, Hodgkin lymphoma and other solid tumors. Kennedy compares the treatment area to a spaceship from a sci-fi movie.

“The machine that takes my scans looks like a little port that you can pass through and it will transport you somewhere,” she says. “They even play the Star Wars theme song to clear everybody out of the room before the treatment begins.”

Opened last fall, the $90 million facility is an engineering marvel in which success relies on both dizzying speed and absolute stillness. Protons moving at 60 percent the speed of light must hurtle toward a target that is utterly still and precisely positioned.

In order to be effective, protons must be accelerated to extremely high speeds. Created from hydrogen gas and guided through a linear accelerator, the protons then pass into a circular device called a synchrotron. The particles whirl around the synchrotron 8 million times per second—the equivalent of 4.5 revolutions of the earth per second. The emerging proton beams attack tumors with exquisite control, thanks to a three-story-tall, 100-ton framework called a gantry, which enables 190-degree rotation around the patient.

Unlike traditional radiation therapy, which passes through both tumor and the healthy tissue beyond it, proton therapy enables clinicians to “paint” the dose, layer by layer, stopping at the tumor’s edge.

Although the proton beam is impressive, Thomas Merchant, DO, PhD, St. Jude Radiation Oncology chair, says it is only one component of a remarkable system.

“It’s not just the beam,” he explains. “It’s everything that surrounds it: How the patient is set up, how the dose is calculated, the imaging that we use to confirm the position of the patient. There’s no room for error here.”

Sub-millimeter accuracy

Today, one of the hospital’s three proton therapy rooms throbs like an artery, rock music pulsing as a new patient, Breydon Hammer, undergoes a rehearsal for treatment that will begin next week. The teen has chosen tunes that put him at ease during the session, in which he discusses his upcoming treatment with a Child Life specialist, two radiation therapists, a radiation oncologist and a radiation physicist. Once all of Breydon’s questions have been answered, he climbs onto the treatment table, nestling into a foam couch that has been customized for his body. An individualized mask stabilizes his head.

As Merchant watches the interaction, he points out attributes of the new system.

“Our verification imaging system is entirely novel,” he observes. “We have the first gantry-independent, robotic cone-CT system ever deployed in a proton therapy setting in the U.S.”

Once Breydon is situated, the only movement is his index finger, tapping a staccato beat as staff members continue their adjustments. Soon, the cone beam CT scanner will produce a 3-D image of his brain.

Clinicians will compare those images to previous scans to ensure that Breydon is in the exact spot for treatment. If minor tweaks are necessary, an automatic patient positioning system will move the couch so that the position is perfect. A special camera system will monitor the couch and do a final correction before treatment begins.

“The patient set-up needs to be accurate, and we have to know the position of the proton beam precisely,” Merchant explains. “It’s not humanly possible to put someone in exactly the same position every day. The system helps correct for variations in day-to-day set-up. Patients lose weight or gain weight; slight shifts can occur. Most proton centers rely on a pair of two-dimensional images to verify the position of the patient. We use the most advanced form of verification imaging, cone-beam CT, to determine a patient’s position for treatment. We believe there is no patient positioning system in the U.S. that is more accurate than the one we have installed in our proton therapy facility.”

As soon as the patient is situated, all staff members leave the room, keeping the child under constant video surveillance throughout the treatment. During the actual proton beam therapy—which lasts only a few minutes—advanced control systems guide the finely focused beams so that they conform to the shape of the tumor. 

Proton pro

Kennedy received proton therapy 38 times, with sessions averaging about 30 minutes from arrival to departure.

“I had the treatment five days a week,” Kennedy explains. “It was weird and not weird at the same time. You lie on this foam bed and they line you up using lasers and CT scans. When it comes time for the actual proton therapy, you can’t feel the protons going in, but you can hear the machine. It’s kind of like the sound a shovel makes as it’s scraping the ground when you’re shoveling snow.”

Kennedy received her treatment in one of the facility’s two gantry rooms, which feature a moveable “scanning” beam. The center also includes a fixed-beam room, as well as anesthesia areas and a recovery room. Families entering the center descend a musical staircase into a rainforest-themed waiting area that was designed with input from parents on the St. Jude Family Advisory Council.

Beam of hope

Editor’s note: Kennedy Adamowich lost her battle with cancer in July 2017.

From Promise, Spring 2016