Endogenous thrombopoietin serum levels during multicycle chemotherapy

Little is known about the behaviour of endogenous thrombopoietin (TPO) seru m levels during rapid sequences of dose-intensified chemotherapy. To charac terize the relationship between TPO levels and platelet counts in this sett ing we serially measured both parameters over the entire treatment period o f patients receiving multicycle polychemotherapy. We found TPO and platelet responses to be generally antagonistic through all cycles, However, a cros s-correlation analysis indicated that TPO responses preceded platelet respo nses by approximately one day in all patients. The cumulative severity of t hrombocytopenia observed over successive cycles was accompanied by an incre asing TPO response which tended to grow overproportionally in relation to t he degree of peripheral thrombocytopenia. These findings are consistent wit h a model suggesting that both platelet and megakaryocyte mass contribute t o a receptor-dependent consumption process regulating the endogenous TPO le vel. In order to develop optimal schedules for exogenous TPO administration it might be important to consider endogenous TPO response characteristics.