118 Chapter 8 Incidence of cardiac toxicity Our literature review on radiation-induced cardiac toxicity in the treatment of oesophageal cancer (EC) revealed crude incidence rates as high as 5-44%[6]. However, the available literature mainly consists of retrospective studies from Asian countries. Prescribed doses were relatively high, and the radiation techniques used were outdated compared to what is considered current standard. For these reasons, toxicity rates may be lower nowadays. Moreover, retrospective studies are often hampered by incomplete follow up data and publication bias, which may cause underreporting of cardiac events. Randomized controlled trials (RCT’s) investigating neoadjuvant chemoradiation followed by surgery versus surgery alone did not report higher cardiac toxicity rates in the neoadjuvant CRT (nCRT) arm as compared to these observed in the surgery alone arm [7]. Although these trials were not powered for detecting differences in cardiac toxicity, the question arises whether cardiac events are really caused by chemoradiation. However, causality with radiotherapy becomes more likely in case of a significant relationship between radiation dose to the heart and cardiac events. There is general consensus that determining the true incidence of radiation-induced cardiac toxicity remains difficult from retrospective studies as cardiac events occur rather frequently in this older population with cardiac risk factors. One would preferably need larger randomized trials or meta analyses “powered” to evaluate toxicity rates. This requires strict follow up and maybe even routine consultations of the cardiologist before and after treatment. An alternative, because of the selection bias in randomised trials, is probably using standardized follow up data and compare this with a non-irradiated EC patient group.
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