Cardiac Morbidity and Radiation Therapy for Breast Cancer

Abstract

The relationship between radiation treatment for breast cancer and subsequent risk of cardiac morbidity and mortality has been known for decades ( 1 Cuzick J. Stewart H. Rutqvist L. et al. Cause-specific mortality in long-term survivors of breast cancer who participated in trials of radiotherapy. J Clin Oncol. 1994; 12: 447-453 Crossref PubMed Scopus (766) Google Scholar , 2 Favourable and unfavourable effects on long-term survival of radiotherapy for early breast cancer: An overview of the randomised trials. Early Breast Cancer Trialists' Collaborative Group. Lancet. 2000; 355: 1757-1770 Abstract Full Text Full Text PDF PubMed Scopus (1195) Google Scholar ), but risks in the modern era are less clear and seem to be significantly lower than in prior eras ( 3 Giordano S.H. Kuo Y.F. Freeman J.L. et al. Risk of cardiac death after adjuvant radiotherapy for breast cancer. J Natl Cancer Inst. 2005; 97: 419-424 Crossref PubMed Scopus (460) Google Scholar , 4 Nixon A.J. Manola J. Gelman R. et al. No long-term increase in cardiac-related mortality after breast-conserving surgery and radiation therapy using modern techniques. J Clin Oncol. 1998; 16: 1374-1379 Crossref PubMed Scopus (165) Google Scholar , 5 Darby S.C. McGale P. Taylor C.W. et al. Long-term mortality from heart disease and lung cancer after radiotherapy for early breast cancer: Prospective cohort study of about 300,000 women in US SEER cancer registries. Lancet Oncol. 2005; 6: 557-565 Abstract Full Text Full Text PDF PubMed Scopus (802) Google Scholar ). There have been significant improvements in technology and awareness, allowing more nuanced dosimetric analysis and attention to cardiac exposure in patients treated with modern computed tomography (CT)–based planning, but long-term follow-up with more modern techniques is limited. Nonetheless, given the excellent long-term survival in breast cancer patients, the impact of cardiac risk on posttreatment survivorship has come to the fore. To date, there are no published randomized radiation studies with an endpoint of cardiac events, though there is a great deal of emerging data on potential surrogates for cardiac risk, such as strain and single photon emission computed tomography imaging ( 6 Lo Q. Hee L. Batumalai V. et al. Subclinical cardiac dysfunction detected by strain imaging during breast irradiation with persistent changes 6 weeks after treatment. Int J Radiat Oncol Biol Phys. 2015; 92: 268-276 Abstract Full Text Full Text PDF PubMed Scopus (34) Google Scholar , 7 Zellars R. Bravo P.E. Tryggestad E. et al. SPECT analysis of cardiac perfusion changes after whole-breast/chest wall radiation therapy with or without active breathing coordinator: Results of a randomized phase 3 trial. Int J Radiat Oncol Biol Phys. 2014; 88: 778-785 Abstract Full Text Full Text PDF PubMed Scopus (48) Google Scholar , 8 Zagar T.M. Kaidar-Person O. Tang X. et al. Utility of deep inspiration breath hold for left-sided breast radiation therapy in preventing early cardiac perfusion defects: A prospective study. Int J Radiat Oncol Biol Phys. 2017; 97: 903-909 Abstract Full Text Full Text PDF PubMed Scopus (54) Google Scholar ). The RADCOMP Pragmatic Randomized Trial of Proton versus Photon Radiation for Stage II-III Breast Cancer is underway (clinicaltrials.gov/ct2/show/NCT02603341) and will report on the relationship between radiation dose to the heart and major cardiac events. In the interim as we await these data, a number of recent publications warrant the attention of the radiation oncologist to inform clinical decisions and radiation planning details.