Study Shows Little Cardiac Risk After Radiation

Breast Cancer Patients Can Be Reassured by New Data

M. D. Anderson researchers have concluded that the risk of ischemic heart disease (narrowing of the arteries) and, ultimately, death after radiation treatment for breast cancer has steadily declined over the last 25 years, according to a study published in the March 16 issue of the Journal of the National Cancer Institute.

This study, the largest and most comprehensive of its kind, offers scientific evidence for what was long thought to be true but never proven: that improvements in radiation techniques and delivery have greatly impacted radiation-associated cardiac mortality, says Sharon Giordano, M.D., the study's lead author and an assistant professor in M. D. Anderson's Department of Breast Medical Oncology.

"Most previous analyses had involved women who had been treated in the 1950s, 1960s and 1970s, decades not considered in the era of modern medicine," Giordano says. "This study should reassure patients that radiation has become safer and there is little, if any, risk of future ischemic heart disease due to having received radiation."

Radiation close to the heart compared

Giordano and her colleagues used data involving 27,283 patients diagnosed from 1973 to 1989 from the National Cancer Institute SEER database (Surveillance, Epidemiology, and End Results), the authoritative source of information on cancer incidence and survival in the United States.

The study compared roughly half of those women (13,998) who had breast cancer on the left side where the heart is located (and where more radiation is delivered to the heart) with 13,285 women who had disease on the right side. "Comparing both gave us a perfect study to examine radiation-induced toxicity and cardiac mortality," Giordano says. Patients also were placed in three groups according to diagnosis date.

Of the women diagnosed from 1973 to 1979, those with tumors on the left side had an increased ischemic heart disease mortality after 15 years (13.1%), compared to patients with tumors on the right side (10.2%). However, of the women diagnosed from 1980 to 1984 and from 1985 to 1989, there was no such difference in cardiac mortality.

The researchers concluded that each year after 1979, the risk of death from ischemic heart disease declined by 6% in women with left-sided breast cancer compared to those with disease on their right side.

Radiation techniques will continue improving

Giordano cautions that because death from ischemic heart disease may not occur until 15 years after treatment, longer follow-up is needed to confirm the risk has been completely eliminated.

The risk of cardiac complications is a great concern to many patients receiving radiation therapy, says Thomas Buchholz, M.D., professor in M. D. Anderson's Department of Radiation Oncology.

"Heart complications associated with radiation treatment really became appreciated in the 1980s, leading to improvements in technique and delivery," Buchholz says. "This study highlights the progress made more than 10 years ago. Receiving radiation will only become safer for patients as we move forward, with newer radiation techniques allowing treatment to exclusively target tumors, while sparing healthy tissue."