Pegfilgrastim-induced fatigue and leukocytosis improved following dose reduction in a young patient with breast cancer: A case report.

Dose-dense (DD) chemotherapy is a treatment option for patients with high-risk premenopausal breast cancer. Pegfilgrastim may be administered as prophylaxis against the development of febrile neutropenia and enables the continuation of the DD schedule; however, it is associated with adverse effects, including bone and muscle pain and fatigue. We herein describe our experience with pegfilgrastim administration alongside DD chemotherapy in a patient with breast cancer. A 29-year-old female patient was diagnosed with locally advanced breast cancer during lactation. The patient was diagnosed with cT2N1M0, stage IIB triple-negative breast cancer and underwent four cycles of DD chemotherapy with epirubicin plus cyclophosphamide, followed by four cycles of docetaxel (DTX) every 2 weeks preoperatively, with 3.6 mg pegfilgrastim administered subcutaneously on day 3 of each cycle. The absolute neutrophil count (ANC) was 2,700, 8,400, 11,100, 13,300 and 15,000/mm³ on day 1 of each cycle. The patient experienced fatigue after each pegfilgrastim injection and was considered to be a high responder to pegfilgrastim. Therefore, 1.8 mg pegfilgrastim on day 3 of the first DD-DTX cycle was recommended. On day 1 of the second cycle, the ANC was 13,090/mm³. The patient experienced less fatigue after the administration of 1.8 mg pegfilgrastim, but there was a significant decline in her performance status. As there is currently no evidence of pegfilgrastim dose reduction to below 1.8 mg, pegfilgrastim was omitted on day 3. On day 14, the patient developed viral enteritis, fever (38°C), and an ANC of 297/mm³. Therefore, the third cycle was postponed. After 1 week, the patient's ANC recovered to 2,480/mm³ and she was administered the third cycle with 3.6 mg pegfilgrastim on day 3. Between January 2015 and March 2018, a total of 55 patients with breast cancer received chemotherapy with pegfilgrastim at the Shiga General Hospital. No patients other than the one presented herein experienced leukocytosis during chemotherapy. Although this was a rare complication, a dose of 1.8 mg pegfilgrastim was effective in palliating the patient's symptoms and preventing DD chemotherapy discontinuation.