Pegfilgrastim-induced hyperleukocytosis leading to hospitalization of a patient with breast cancer

In patients receiving dose-dense chemotherapy, adverse effects such as neutropenia can be reduced by colony-stimulating factors. Pegfilgrastim, a colony-stimulating factor, has associated adverse effects, including bone pain, fever, and, rarely, hyperleukocytosis. We describe a 45-year-old woman with breast cancer receiving dose-dense Adriamycin and cyclophosphamide chemotherapy. She presented with hyperleukocytosis after receiving pegfilgrastim, which resulted in hospitalization. This case report reviews the strategy to minimize the risk of hyperleukocytosis from pegfilgrastim administered in dose-dense chemotherapy.