Scripps Opens Region’s First Proton Therapy Center for Cancer Care

The primary benefit of proton therapy is its ability to treat patients with a substantially lower total radiation dose to normal tissue, compared to the latest X-ray technology. “X-rays penetrate entirely through the body, whereas a proton beam can be controlled to stop where the tumor stops,” said Carl Rossi, MD, the center’s medical director. “This is important, because less radiation to healthy tissue means patients are more likely to tolerate their treatments better and are less likely to have problems in the long run related to their treatment.”

For example, compared to X-rays, a proton beam can effectively target prostate cancer tumors with less exposure to the bladder, rectum and small intestine. With breast cancer, it can treat the left breast without exposing the heart to radiation. And with lung cancer, protons will spare more of the patient’s spinal cord, esophagus and bone marrow.

“For children with specific types of tumors, proton therapy is particularly effective because it is very targeted and spares healthy, developing tissue from further damage. It has been found to be particularly effective in brain tumors where secondary radiation can lead to learning disabilities, reduced IQ scores and other potential lifelong side effects. Proton therapy can also reduce the long-term likelihood of secondary radiation-induced tumors,” said Donald B. Kearns, M.D., acting president of Rady Children’s Hospital-San Diego.

Because of its exceptional accuracy, proton therapy can in some cases enable doctors to safely deliver a higher daily dose of radiation to the tumor than is possible with X-rays. This technique, known as hypofractionation, can translate to faster cancer control and fewer treatment sessions.

Today, most proton therapy is delivered using the traditional “passive scatter” approach, in which the beam is shaped to match the tumor after exiting the treatment nozzle. With passive scatter, the beam passes through specially manufactured devices to form the beam’s height, width and penetrating depth, before entering the patient.

The Scripps center will be the nation’s first to exclusively treat patients with pencil-beam scanning, which is more precise and versatile than passive scatter. Instead of using physical devices outside of the treatment nozzle, pencil-beam technology electromagnetically shapes the beam inside the nozzle via computerized data files, developed from 3-D models of patients’ tumors.

Pencil beam technology links patient data files to electromagnets inside the nozzle to sweep the beam across the tumor, building up the radiation dose onto the tumor layer by layer. The penetrating depth of the beam is controlled digitally by an energy selection system, which varies the energy of the protons.

“We’re essentially breaking down each tumor into thousands of tiny cubes, and then ‘painting’ each individual cube with radiation,” said Dr. Rossi, who has treated more than 9,000 prostate cancer patients with proton therapy. “This approach spares even more normal tissue and enables us to treat larger and more irregularly shaped tumors than possible before. It also produces far fewer neutrons than passive scatter, which further reduces the probability of secondary malignancies. And it allows us to adapt treatment plans more quickly, as tumors change during the course of treatments.”

The center’s proton delivery system is both refined and powerful. Its technological centerpiece is a 95-ton superconducting cyclotron, where the proton beam is generated using hydrogen and oxygen to create a plasma stream. Protons are extracted and accelerated to roughly 100,000 miles per second. They are then delivered to a beam transport system, which uses a series of high-powered electromagnets to steer and transport the beam to one treatment room at a time using a vacuum line.

Varian Medical Systems of Palo Alto, Calif., developed, installed and validated the center’s ProBeam proton delivery system, which received clearance from the Food and Drug Administration earlier this year.

Research studies have shown the effectiveness of proton therapy in treating a variety of tumors – particularly solid, localized tumors that are surrounded by critical organs. These include tumors of the prostate, head and neck, breast, spine, lung and gastrointestinal tract, among others. Protons are also the preferred form of radiation for many childhood cancers because growing bodies are especially sensitive to the potential short- and long-term side effects of radiation.

Scripps Proton Therapy Center is designed with five treatment rooms, three of which include gantries, which rotate around the patient 360 degrees to allow treatment from any direction. The center’s other two rooms are designed with fixed-beam machines. The facility is currently treating patients in select rooms and projects commissioning and clinical use of all treatment rooms in 2014. The center offers on-site access to the sophisticated imaging technology needed for accurate tumor targeting, including CT and PET-CT scanners and an MRI machine.

Scripps Proton Therapy Center is designed to provide a comforting, emotionally supportive environment for healing. This includes a lobby with large expanses of glass for natural day lighting, modular stone walls and wood and tile design accents. Children and their families will have access to special areas designed specifically for pediatric patients, including a dedicated entrance, anesthesia area and recovery room.

Scripps Proton Therapy Center is located at 9730 Summers Ridge Road, San Diego 92121.

Some 1.7 million new cancer cases are projected in the United States in 2014, according to the American Cancer Society. Approximately two-thirds of all cancer patients receive some form of radiation therapy during their illness.

“We’re encouraged to see that overall cancer survivor rates in America have improved from about 50% in the 1970s to almost 70% today,” said Jeff Bordok, CEO of Advanced Particle Therapy, the center’s developer and owner. “As more survivors are moving on to a life after cancer, we need to be cognizant of the effects that unnecessary radiation exposure may have on their health and well-being years down the road, such as chronic disease or treatment-related cancers. The precision offered by proton therapy means patients may enjoy a healthier survivorship later.”

A noninvasive therapy, proton treatments are delivered on an outpatient basis and most patients receive daily weekday treatments for four to eight consecutive weeks. Patients feel no physical sensation during treatments and are free to go about their daily activities following therapy. (Pediatric patients may receive their treatment under anesthesia.) Time spent in the treatment room is usually about 15 to 25 minutes, most of which is for patient positioning and equipment adjustments.

Learn more about Scripps Health, an integrated health care system in San Diego, Calif.

Stephen Carpowich
858-678-7183
carpowich.stephen@scrippshealth.org
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