Safety of AlloPBPCT donors: biometrical considerations on monitoring long term risks.

Up to now there are no data on long-term effects of allogeneic peripheral blood cell transplantation (AlloPBPCT). In particular, long term effects on healthy donors by the mobilization procedure which includes the exposition to G-CSF over several days are unknown. Recently the possibility of an increase in risk for acute leukaemia in this cohort has been discussed. Systematic long-term safety monitoring for AlloPBPCT donors cannot be adequately planned without agreeing on a both relevant and reasonably pessimistic hypothetical size of the increased leukaemia risk to be detected if present. Using data on leukaemia after treatment for Hodgkin's disease as example it is argued that a) excess leukaemia cases should be expected to occur predominantly between 2 and 10 years after the leukaemogenic event and b) a reasonably pessimistic guess would expect about 0.5% leukaemia cases at 10 years in AlloPBPCT donors. Such a tenfold increase over the general population's 10 year leukaemia incidence would be relevant, but require long-term follow up of several thousands of donors to demonstrate or exclude. In conclusion, safety monitoring for AlloPBPCT donors can only be organized on an international scale.