The timing of chemotherapy-induced neutropenia and its clinical and economic impact.

Chemotherapy-induced neutropenia (CIN) and its complications exact a substantial toll on patients with cancer. Febrile neutropenia (FN), a sign of life-threatening infections, is associated with lengthy hospitalizations, early mortality, and high medical costs. In addition, neutropenia is the primary cause of dose reductions and dose delays, limiting the delivery of the chemotherapy at full dose and on schedule and thus compromising long-term survival in patients with potentially curable malignancies. Many recent studies in several major tumor types have documented that the greatest risk of neutropenia and its complications is in the first cycle of chemotherapy, with more than 50% of the first episodes of neutropenia and FN occurring in the first cycle. In addition to their other negative effects, these first-cycle events are also associated with early termination of the chemotherapy. The disproportionately high risk of neutropenia in the first cycle has important implications for managing CIN, as well as for the development and use of guidelines for supportive care. It highlights the importance of determining which patients are at high risk for neutropenia and its complications before the chemotherapy is initiated and implementing interventions, such as prophylactic growth factor support in the first and subsequent cycles, to reduce that risk.