Cardiac late effects are a major health concern for long-term survivors after radiotherapy for breast cancer. Large cohort studies to better understand the exact dose–response relationship require individual estimates of radiation dose to the heart. To predict individual cardiac dose from information that is typically available for all members of a retrospective epidemiological cohort study, 774 female breast cancer patients treated with megavoltage tangential field radiotherapy in 1998–2008 were examined. All dose distributions were calculated using Eclipse with the anisotropic analytical algorithm (AAA) for photon fields and the electron Monte Carlo algorithm for electron boost fields. Based on individual dose volume histograms, the authors calculated absorbed dose in the complete heart as well as in six functional substructures. Statistical models were developed to predict absorbed dose using only covariate information from patients’ clinical records on tumor location, patient anatomy and radiotherapy prescription. The out-of-sample prediction error for mean heart dose was 54% (coefficient of variation). The prediction error in functional substructures ranged from 49–68% for mean dose and from 52–86% for extreme dose. The authors conclude that based on a patient sample with exact heart dosimetry, it is possible to use clinical information alone to predict absorbed heart dose in the remaining cohort with a quantified error suitable for dose–response analyses of cardiac late effects.
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*Institute for Medical Biostatistics, Epidemiology and Informatics, University Medical Center Mainz, Mainz, Germany; †Department of Radiation Oncology, University Medical Center Mainz, Mainz, Germany; ‡Department of Radiation Oncology, University Hospital Ulm, Ulm, Germany.
The authors declare no conflicts of interest.
For correspondence contact: Daniel Wollschläger, Institute for Medical Biostatistics, Epidemiology and Informatics, University Medical Center Mainz, Obere Zahlbacher Str. 69, 55131 Mainz, Germany, or email at email@example.com.
(Manuscript accepted 26 July 2016)
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