That finding comes from researchers at Harvard and Massachusetts General Hospital in Boston.
"This study could have a substantial impact on the care of patients," researcher Nancy Tarbell, MD, of Massachusetts General Hospital, says in a news release.
Radiation therapy is often used to reduce the chance of cancer recurrence. Proton beam therapy focuses the radiation very tightly to reduce impact on normal tissue around tumors. Proton therapy isn't widely available in the U.S.; most cancer patients get other types of cancer radiation therapy.
Tarbell's team compared the medical records of 503 cancer patients treated with proton therapy at Harvard from 1974 to 2001 to the medical records of 1,591 cancer patients treated with other types of radiation therapy.
The patients, who had been matched based on their cancer type, age, and other factors, were followed for at least a year after treatment, and typically for six to seven years.
During that time, most of the patients didn't develop another cancer, regardless of the type of radiation therapy they got. But new cancers were less common in the patients who got proton therapy radiation -- 6.4% of them developed another cancer, compared with 12.8% of patients who got other types of radiation.
The researchers, who presented their study today in Boston at the American Society for Therapeutic Radiology and Oncology's annual meeting, caution that the findings need to be confirmed and ongoing studies are needed because cancers can take many years to develop.