Estimating the Risks of Radiation for Breast Cancer Patients with Cardiovascular Risk

Cardiovascular Event-free Survival after Adjuvant Radiation Therapy in Breast Cancer Patients Stratified by Cardiovascular Risk
October 2014
Onwudiwe, N. C., Kwok, Y., Onukwugha, E., Sorkin, J. D., Zuckerman, I. H., Shaya, F. T. & Daniel Mullins, C.
Cancer Medicine
IMPAQ Health
Onwudiwe, N. C., Kwok, Y., Onukwugha, E., Sorkin, J. D., Zuckerman, I. H., Shaya, F. T. & Daniel Mullins, C. (2014). Cardiovascular event-free survival after adjuvant radiation therapy in breast cancer patients stratified by cardiovascular risk. Cancer Medicine, 3(5), 1342-1352.

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.