The recent report by Hawkins and colleagues from the Childhood Cancer Research Group in Oxford describes the risk of bone cancer in over 13000 children who survived three years after treatment. Hawkins et al emphasize the need to put the risks in perspective. But from the patient's perspective, the relevant statistic is the cumulative probability or the absolute risk of developing a second cancer. Reports on large populations of patients have shown that the cumulative probability of second cancer can be quite low. Despite this low absolute risk, high priority should be given to characterizing and preventing second neoplasms because they are often associated with high levels of morbidity and mortality.
Several questions remain regarding the future risk of cancer in child survivors.
While the risk of leukemia associated with alkylating agents seems to be restricted to the first decade after exposure, data suggest that radiation will play a substantial role in the risk of non-leukaemic malignancies two and more decades later. The possibility of interactions between radiation and some chemotherapeutic agents has been suggested. However, testing for such interactions often requires large study populations, which up until now have been scarce. As the report by Hawkins et al confirms, patients with hereditary retinoblastoma who have received radiation exposure are at massively increased risk of developing a subsequent bone tumor. Other genetic characteristics that may interact in this way include p53, ATM, and GST null phenotype.