European Heart Journal Advance Access originally published online on September 13, 2007
European Heart Journal 2007 28(21):2689; doi:10.1093/eurheartj/ehm387
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Acute chromosomal DNA damage after radiation exposure: reply
CNR
Institute of Clinical Physiology
Pisa
Italy
CNR
Institute of Clinical Physiology
Pisa
Italy
E-mail address: andreas{at}ifc.cnr.it
We are grateful to Dr Yildiz and colleagues for their interest in our article. Their letter offers a unique opportunity to clarify several important points. First of all, it is important to focus on the physical dose–biodosimetric data correlation. In the original version of the manuscript, we indeed presented the data on the (lack of) correlation between Dose-Area Product and increase in micronuclei, but we were gently forced to delete them in the Revision process. As Reviewer 1 put it, ‘no correlation between the radiation and the change in MN can be found due to the restricted sample size’, and therefore ‘the issue should not be mentioned in any part of the manuscript’. And he was probably right! For any given dose, the amount of damage is modulated by several other factors: reactive oxygen species after coronary revascularization and levels of myocardial damage (as Dr Yildiz et al. nicely pointed out); amount of contrast (which sensitizes lymphocytes to radiation damage); environmental mutagens (such a smoking); and perhaps most importantly, polymorphism of genes involved in DNA damage and repair.1 That is why all the literature describes a weak, if any, correlation between physical dose and biodosimetric damage in the low dose range of acute and chronic exposures.1 We also agree that the increase of frequency of micronuclei in circulating lymphocytes would have been significant after coronary angiography with a larger sample size. But above and beyond these important statistical aspects, the challenge ahead is to identify the determinants of damage, eventually translating an estimate of population risk into an individually tailored radio-risk profile through biodosimetry. One might ask: Why to discuss these biodosimetric issues in a top cardiology journal? Cardiologists prescribe and/or practice > 50% of all medical imaging examinations, accounting for about two-third of the total effective dose, which in US totals the dose equivalent of 160 chest x-rays per head per year to the average citizen.2 In April 2007, the American College of Radiology released the landmark ‘White Paper on Radiation Dose in Medicine’, concluding that ‘the expanding use of imaging modalities may result in an increased incidence of radiation-induced cancer in the not-too-distant future’.3 Cardiology is the epicentre of the radiological tsunami of the last 20 years, and the current cardiological practice is based on a deregulated, radiation-insensitive, and imaging prescription.4 Biodosimetry may help the scientist to shrink uncertainties still surrounding low dose effects1,5 and the clinicians to ‘see’, directly on their patients, the radiation damage through biomarkers of somatic DNA damage, which are intermediate endpoint of carcinogenesis and long-term predictors of cancer. Eventually, this will help the cardiologist to include the long-term risk in the risk-benefit balance, quintessential to determining the appropriateness of a diagnostic and therapeutic procedure, especially considering that more than one third of testing—even without considering radiation risk—are inappropriate in modern cardiology.6 It's not radioprotection, it's cardiology!
References
- Andreassi MG. The biological effects of diagnostic cardiac imaging on chronically exposed physicians: the importance of being non-ionizing. Cardiovasc Ultrasound (2004) 2:25.[CrossRef][Medline]
- Mettler FA Jr. Report from National Council on Radiation protection. (2007) April 16. Diagnostic Imaging Online.
- Amis ES Jr, Butler PF, Applegate KE, Birnbaum SB, Brateman LF, Hevezi JM, Mettler FA, Morin RL, Pentecost MJ, Smith GG, Strauss KJ, Zeman RK. American College of Radiology white paper on radiation dose in medicine. J Am Coll Radiol (2007) 4:272–284.[CrossRef][Medline]
- Picano E. Sustainability of medical imaging. Education and Debate. BMJ (2004) 328:578–580.
[Free Full Text] - Committee to Assess Health Risks from Exposure to Low Levels of Ionizing Radiation; Nuclear and Radiation Studies Board, Division on Earth and Life Studies, National Research Council of the National Academies. Health Risks From Exposure to Low Levels of Ionizing Radiation: BEIR VII Phase 2. (2006) Washington, DC: The National Academies Press.
- Redberg R. The appropriateness imperative. Am Heart J (2007) 154, Editorial. 201–202.[CrossRef][Medline]
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