The authors of this research note that the role of radiotherapy and chemotherapy in the development of secondary tumours in long-term survivors of childhood cancer is well established, and that research is now focusing on the long-term treatment-related effects other than cancer.  Although effects of radiotherapy and the dose of different chemotherapy drug classes on cardiac mortality has been assessed by some, the authors note that there has been no evaluation of the detailed effects of radiation (dose received by the heart), to their knowledge.  

This study was conducted to assess the role of treatment on the long-term overall survival and cardiovascular mortality, using a cohort of 5-year survivors of a childhood cancer diagnosed before 1986 in France and the UK (n=4,122).  Participants were observed for a median of 26 years (range 5-60).  The main results were as follows:

• 603 deaths occurred during 86,453 person-years of follow-up, for an overall standardised mortality ratio (SMR) that was 8.3-fold higher (95% CI, 7.6-fold to 9.0-fold higher) in relation to the general populations in France and the UK.

• Individuals in this cohort were five-fold more likely to die as a result of cardiovascular diseases (n=32) and were 5.8-fold more likely to die as a result of cardiac diseases (n = 21)

• The risk of dying as a result of cardiac diseases was higher in individuals who had received a cumulative anthracycline dose greater than 360 mg/m2 (RR 4.4; 95% CI 1.3 to 15.3)

• The radiation dose delivered to the heart was estimated for 2,870 patients who had received radiotherapy; the risk of cardiac mortality was higher in individuals who received an average radiation dose that exceeded 5 Gy (RR 12.5 and 25.1 for 5 to 14.9 Gy and > 15 Gy, respectively)

The author of an accompanying editorial comments that the study confirms the association between cardiovascular mortality and anthracyclines; however the striking finding is that as little as 5 Gy of radiation to the heart increases the risk of cardiovascular mortality, even after adjustment for other factors.  Due to other research findings, they caution that this should not be interpreted to mean that doses lower than 5 Gy are harmless, although they do appear to decrease the risk. They also discuss the prevention and management of anthracycline cardiomyopathy, noting that primary prevention is essential, and that they have encouraged the use of dexrazoxane on childhood cancer protocols using anthracyclines.