Rates of myocardial infarction and coronary artery disease and risk factors in patients treated with radiation therapy for early-stage breast cancer

Authors

  • Reshma Jagsi MD, DPhil,

    1. Radiation Oncology Department, University of Michigan School of Medicine, Ann Arbor, Michigan
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    • Author contributions are as follows. Dr. Jagsi: conception and design, acquisition of data, analysis and interpretation of data, drafting of the article. Mr. Griffith: acquisition of data, analysis and interpretation of data, critical revision of article, statistical analysis. Dr. Koelling: conception and design, critical revision of article. Ms. Roberts: acquisition of data, critical revision of article. Dr. Pierce: conception and design, analysis and interpretation of data, critical revision of article, administrative/technical/material support, supervision. There was no specific funding source for this project, beyond general funding by the University of Michigan. Drs. Jagsi and Pierce had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis

  • Kent A. Griffith MS,

    1. University of Michigan Cancer Center Biostatistics Core, Ann Arbor, Michigan
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    • Todd Koelling MD,

      1. Internal Medicine Department, University of Michigan School of Medicine, Ann Arbor, Michigan
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      • Rachel Roberts BS,

        1. Radiation Oncology Department, University of Michigan School of Medicine, Ann Arbor, Michigan
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        • Lori J. Pierce MD

          Corresponding author
          1. Radiation Oncology Department, University of Michigan School of Medicine, Ann Arbor, Michigan
          • Radiation Oncology Department, University of Michigan School of Medicine, Ann Arbor, Michigan 4308 Cancer and Geriatrics Center, 1500 E. Medical Center Dr., Ann Arbor, MI 48109-0010
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          • Fax: (734) 647-9654


        • Presented in preliminary (abstract) form at the annual meeting of the American Society of Therapeutic Radiology and Oncology, November 2006.

        • The authors confirm that this is original, unpublished work and that no conflicts of interest exist.

        Abstract

        BACKGROUND.

        Radiation therapy (RT), a critical component of breast-conserving therapy for breast cancer, has been associated with coronary artery disease (CAD) in numerous older studies, but the risk may be lower with modern techniques.

        METHODS.

        Observed rates of cardiac events in 828 patients treated with breast-conserving surgery and RT at the University of Michigan were compared with expected rates. Relations between potential risk factors and actuarial rates of first CAD event were analyzed.

        RESULTS.

        Observed risks of cardiac events were lower than expected. The standardized incidence ratio (SIR) of myocardial infarction (MI) was 0.44 (95% confidence interval [CI]: 0.21–0.70). The SIR of MI or CAD requiring intervention was 0.50 (95% CI: 0.27–0.68). With a median follow-up of 6.8 years, 12 (1.4%) patients had at least 1 MI on follow-up and 20 (2.4%) had at least 1 MI or CAD requiring intervention. Median age at first cardiac event was 75.9 years (range, 43.1–91.5). Median interval from RT to occurrence of the first cardiac event was 3.7 years (range, 13 days to 15.4 years). The 10-year cumulative incidence of MI was 1.2% and cumulative incidence of MI or CAD requiring intervention was 2.7%. On multivariate analysis, age, diabetes mellitus, active smoking, and laterality of RT were significant predictors of MI. Age and active smoking were significant predictors of MI or CAD requiring intervention.

        CONCLUSIONS.

        Patients in this series had lower risk of ischemic cardiac events than expected. Although small in absolute magnitude, patients radiated to the left side did have a statistically significant increased risk of MI. These findings support further investigation of techniques to minimize the long-term cardiac risks faced by breast cancer patients. Cancer 2007 © 2007 American Cancer Society.

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