Though deaths from breast cancer are declining in the United States, older women who survive early-stage breast cancer are at risk of dying due to cardiovascular disease. To build upon prior research, Ilene Harris collaborated in a study of a population of elderly women with breast cancer and varying cardiovascular risks. The purpose of this study was to estimate the risk of a cardiovascular event or death associated with modern radiation therapy. Researchers used data from the linked Surveillance, Epidemiology, and End-Results (SEER)-Medicare database.
This study focused on women aged 66 and older with stage 0-III breast cancer, who were diagnosed between 2000 and 2005. These women were broken into cohorts based on their cardiovascular risk (low, intermediate, or high). To estimate the risk of a combined outcome of hospitalization due to cardiovascular event or death within 6-24 months of diagnosis, researchers used a multivariable Cox model. Researchers observed 91,612 women, 43.2 percent of whom were treated with radiation therapy and 56.8 percent of whom were not.
Results indicated that for women deemed high- or intermediate-risk, receiving radiation therapy within the first 6 months of diagnosis was associated with a significant increased risk for the combined outcome. Women deemed low-risk did not experience this increased risk of being hospitalized for a cardiovascular event or dying 6-24 months after diagnosis. Researchers therefore concluded that the cardiovascular medical histories of women seeking radiation therapy for stage 0-III cancer should be taken into consideration by providers. Because these women are at an increased risk for one of the above-mentioned events, they should be monitored for at least 6 months after radiation treatment, possibly more.