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Risks of heart disease after radiotherapy.

Year: 2011
Type: article
Abstract: Heart disease and cancer are the 2 leading causes of morbidity and death worldwide.1 The prognosis of many cancers has improved, and an increasing number of patients go on to live for many years as cancer survivors. More than 50% of cancer patients receive radiotherapy during treatment, and it is well established that therapeutic irradiation can result in late cardiovascular morbidity and death.2 Much of the evidence for this risk comes from patients treated decades ago for Hodgkin lymphoma (HL) using older radiotherapy techniques.3 Although more modern treatment often involves lower cardiac doses and can therefore result in lower risk, there is evidence that an increased risk of cardiac morbidity remains for HL patients treated more recently4 and might also remain for patients who are being treated today, whether for HL or for some other cancers, such as breast cancer. In the past, the heart was thought to be relatively resistant to the effects of radiation and damaged only by doses of ≥30 Gy. More recent data from several independent sources have provided substantial evidence that mean heart doses of ≤20 Gy, and even ≤5 Gy, can increase the risk. These sources include information pertaining to atomic bomb survivors5 and patients treated for childhood cancers,6 peptic ulcer disease,7 and breast cancer.8,9 Data from the Early Breast Cancer Trialists' Collaborative group include women who were randomized within trials to radiotherapy or no radiotherapy. Retrospective estimation of mean heart doses, by 3-dimensional reconstruction of radiotherapy techniques specified within the trial protocols, yields an increase in relative risk of cardiac death of 3.1% per Gy.10 Modern techniques of radiation therapy, such as intensity-modulated radiotherapy (IMRT) and tomotherapy, enable radiation oncologists to deliver doses with far more accuracy than was previously possible. Unfortunately, these techniques have advanced beyond the current knowledge of normal cardiovascular tissue complications. The critical dose and volume relationships for individual cardiac structures, and for individual cardiovascular endpoints, are not known with any accuracy. For example, it is not known whether it might be advantageous to deliver a high dose to a small volume of the heart or a smaller dose to a larger volume of the heart. There is a general view that the avoidance of cardiac doses of >30 Gy will eliminate any significant risk of late effects, but evidence for increased risks from lower doses, as described above, appears to contradict this. In addition, only limited data are available, as yet, on the potential interactions of radiation, both with drug treatments (such as anthracyclines and tyrosine kinase inhibitors) and with conventional cardiovascular risk factors (such as smoking and hypertension). These data will be essential to enable the accurate prediction of risks on an individual basis. The study of radiation-induced cardiovascular effects is complicated by the wide spectrum of disease that can occur, including coronary artery disease, pericardial disease, valvular disease, and cardiomyopathy.2 It is further complicated by the prolonged latency of many of the endpoints. This necessitates the imaginative use of a variety of scientific approaches and data sets in attempts to answer the outstanding questions. The development of validated early-surrogate markers of late cardiovascular risks, perhaps by using modern imaging techniques such as cardiovascular magnetic resonance, might also prove vital to the more rapid acquisition of data relevant to modern treatments. At present, the clinical relevance of recognized early abnormalities, such as perfusion defects after breast cancer treatment,11 is unknown. It is also not known whether interventions after exposure—for example, with antiplatelet drugs, angiotensin-converting enzyme inhibitors, or statins—may lower cardiovascular risks. Improved knowledge in the emerging field of onco-cardiology is important for numerous reasons: 1) to better inform patients of risks during consent; 2) to enable informed management decisions that are based on the risks of late effects, as well as on oncologic effectiveness; 3) to aid radiotherapy planning in the era of sophisticated dose delivery; and 4) to enable, for cancer survivors, better targeted follow-up, screening, and intervention. It is vital to pay appropriate attention to the risks of heart disease after radiotherapy.
Language: English
Field: Medicine
Open Access status: green
OpenAlex ID: W1626697859
FWCI: 0.859
Cites: 10
Cited by: 24
Related to: 10