Proton Therapy Uses, Benefits in Fighting Cancer

Proton Therapy brings new level of precision to cancer care in San Diego



Carl Rossi, M.D.

San Diego County is fertile ground for both high–quality health care and scientific innovation. So it was fitting when the region became home to one of the most technologically advanced cancer treatment centers in the nation last year with the opening of the Scripps Proton Therapy Center.

Proton therapy is an extremely precise form of external beam radiation treatment that effectively kills tumors while sparing more of a patient’s healthy tissue than conventional X–ray radiation. 

This accuracy is important because less radiation to healthy tissue lowers the probability of patients experiencing side effects and treatment–related cancers.

Breast cancer is top–of–mind in October during national Breast Cancer Awareness Month—and proton therapy effectively treats this condition, along with many other forms of cancer.

Approximately two–thirds of all cancer patients will receive some form of radiation therapy during their illness, according to the American Society for Radiation Oncology.

How does proton therapy work?

Proton therapy is delivered by generating a beam that penetrates the body from the outside. Because the beam is composed of protons—positively charged subatomic particles—the radiation dose can be controlled to conform to the shape and depth of the tumor site. Protons stop where the tumor stops. By comparison, X–ray radiation therapy beams, which are most commonly used today, penetrate well beyond the tumor because they have no electrical charge.

What types of patients are candidates?

Proton therapy is best suited for solid tumors that have not spread to distant areas of the body, are located near sensitive normal tissue and require high doses of radiation. Proton therapy is also recognized as the preferred form of radiation therapy for many pediatric cancers, since children’s bodies are still growing and are extremely sensitive to the harmful effects of radiation. A recent national survey led by Scripps showed that the number of pediatric patients treated with proton therapy annually has increased by 36% since 2010.

The center has received patients both from within the Scripps Health system and through its affiliate providers, Rady Children’s Hospital-San Diego and UC San Diego Health System. Treatment at Scripps Proton Therapy Center is available to any health system in San Diego and beyond. More than one–third of Scripps’ proton patients to date have come from outside San Diego, including nine different states and as far away as Monaco and China.

What are proton treatments like?

During therapy, patients feel no physical sensation from the proton beam, hear very little noise and experience minimal discomfort while on the treatment table. The delivery of the proton beam to the patient typically lasts approximately one minute per treatment field. Time spent in the treatment room is usually about 15 to 20 minutes, most of which is for precise patient positioning and equipment adjustments. Afterward, patients are free to go about their daily activities, although pediatric patients may receive treatments under anesthesia. Proton treatments are delivered on an outpatient basis and most patients receive daily weekday treatments for four to eight consecutive weeks.

Who has benefited so far?

Scripps has branched out quickly to treat a wide variety of cancer types. Tumor sites treated since the center’s opening include lung, brain, spinal column, base of the skull, head and neck (e.g., oropharynx, salivary gland), central nervous systems, pancreas, rectum, esophagus, breast (male and female), testis, prostate, inter–abdominal lymphoid tissue, thymus gland, bone and others. The center has also delivered a number of re-treatments in areas where patients had prior radiation (an application where protons are especially appealing, because less healthy tissue is exposed to additional radiation). Doctors have also treated a number of non–cancerous tumors.

Any personal stories to share?

Anastasia Berkheimer is a 71–year–old woman who came to us with left–side breast cancer and a pre-existing heart condition. Research published in the New England Journal of Medicine has shown that women who received X–ray radiation to their left breast developed a higher risk for heart disease, which was directly linked to the volume of heart being irradiated during treatment. Anastasia chose proton therapy because it could treat the tumor area without affecting her heart at all. Anastasia successfully completed treatments in just two weeks with minimal side effects and is back to her passion of playing in a ukulele band to raise spirits at local senior citizen homes.

Is Scripps different from other proton centers?

There are now more than 17 proton therapy centers in the United States, but only Scripps and Mayo Clinic treat patients 

exclusively with pencil-beam scanning technology, a completely digitized delivery system. With pencil–beam scanning, doctors create 3–D models of each tumor and convert them into computerized data files. The technology breaks each tumor into thousands of tiny cubes, and then uses electromagnets to sweep the proton beam across the tumor, treating it layer by layer, to the precise height, width and depth prescribed by the physician. This approach is considerably more accurate than previous generations of proton technology.

Will the center take part in research?

As a member of the Proton Collaborative Group (PCG), Scripps Health is participating in multi–institutional research studies to help optimize proton therapy. Currently, Scripps is part of a PCG registry trial to gather clinical outcome data from all of its patients, regardless of diagnosis, and expects to expand into tumor–specific studies. Scripps also plans to be involved in prospective randomized research trials comparing proton and X–ray radiation therapy through its involvement with NRG Oncology, a collaborative research organization of the National Cancer Institute.

Is the treatment covered by insurance?

Proton therapy has been approved by the Food & Drug Administration since the first hospital–based proton center in the U.S. opened in 1990. It has an established history of reimbursement by Medicare and many private health insurance payers. Specific coverage guidelines vary among commercial insurers.

Scripps Health provides the Center’s clinical management services and Scripps Clinic oversees the medical services. Advanced Particle Therapy is the center’s developer and owner. Varian Medical Systems of Palo Alto, California developed, installed and validated the center’s ProBeam proton delivery system. The center is located in the Mira Mesa area of San Diego at 9730 Summers Ridge Road. More information is available by calling 858-549-7400.

Carl Rossi, M.D. is a radiation oncologist and medical director of the Scripps Proton Therapy Center who has more than 20 years of experience with proton therapy.