By Leonard Arzt

Recent research has demonstrated that treating breast cancer patients with conventional radiation may cause significant damage to their hearts. Fortunately, proton therapy offers a safe and effective alternative to conventional radiation. Proton radiation treats breast cancer without damaging the underlying tissues, including the heart, so that women no longer have to risk their hearts to treat their cancer.

As Dr. Carl Rossi, medical director of the Scripps Proton Center, San Diego, Calif., said, "The risk of treating women with breast cancer with conventional radiation is not trivial, nor are the costs to the patient and to society."

In a study published in the New England Journal of Medicine in 2013, researchers analyzed the medical records of thousands of women who had been treated with conventional radiation for breast cancer over the last 40 years. The study revealed that as the years passed, these patients were at an increasing risk of developing heart disease and often needed to undergo expensive, difficult treatment like bypass surgery or angioplasty as a result. Their risk of experiencing these serious complications was directly related to the volume of the heart that was irradiated, and the total radiation dose that the heart received.

A research letter published in the JAMA Internal Medicine in 2013 estimated that the increased lifetime risk for a heart attack or other major heart event in women who had traditional radiation for breast cancer is between 0.5 percent and 3.5 percent, with women who had traditional radiation on the left breast at the highest risk because of the heart's position on the left side.

Dr. Rossi said, "Because of the shape of the breast and the chest wall and because of the fact that the conventional X-rays do not stop where you would like them to stop, in many cases, when you treat the breast with X-rays, you end up radiating a varying portion of the underlying heart, and when you radiate the heart you cause irreversible damage to the blood vessels and the heart muscle."

Unlike conventional X-ray therapy, proton therapy uses high speed particles that can be more precisely conformed to treat the tumor while sparing healthy tissue and without an exit dose. "Proton therapy for breast cancer allows clinicians to more carefully target the radiation and stop the protons before hitting the heart," Dr. Rossi says, "In many cases we can reduce the radiation dose to the heart to zero. Zero radiation equals zero chance of developing a radiation-induced side effect."

In some cases, proton therapy is the only radiation available to breast cancer patients suffering a recurrence. In an interview at the National Proton Conference, Dr. Marcio Fagundes, medical director of the Provision Center for Proton Therapy, Knoxville, Tenn., said, "Women who have received prior radiation to the breast or the chest wall after a mastectomy may develop a recurrence where the tumor comes back in the lymph nodes behind the sternal bone, the internal mammary nodes located right on top of the heart. This is an area that is very difficult to treat if you're not using a tool like proton therapy that can selectively deposit the dose right there. We can do the treatment and not expose the heart and selectively deposit the dose right there. So that is a subset of patients for whom proton therapy may be the only way to treat them."

Proton therapy is not only effective for breast cancer, but for many other adult and pediatric cancers. There are currently 14 operating proton therapy centers in the U.S., with about a dozen more in development. For more information on proton therapy, visit www.proton-therapy.org.