[Timing of Administration of Pegfilgrastim and Prophylaxis for Febrile Neutropenia for Patients with Early Breast Cancer Receiving Chemotherapy].

Febrile neutropenia(FN)causes a prolonged treatment schedule and decreased relative dose intensity(RDI)during cancer chemotherapy, which adversely affects prognosis. In recent years, dose-dense(dd)chemotherapy has been used as adjuvant chemotherapy for patients with breast cancer based on the results of improved disease-free survival according to meta-analysis data. Regarding neoadjuvant chemotherapy for human epidermal growth factor receptor 2-positive breast cancer, taxanes and trastuzumab with the addition of pertuzumab have shown higher pathological complete response rates and elevated incidences of FN. One hundred seventy-six patients received pegfilgrastim(PEG)prophylaxis between January 2011 and January 2023. Until 2019, the median day of PEG prophylaxis was day 4 from chemotherapy completion(days 2- 3, 14 cases; day 4, 41 cases; and day 5, 8 cases)with antibiotic prophylaxis in 58 patients(92%). FN was observed in 19 cases(30%). The RDIs of TC and FEC were 96.8% and 96.0%, respectively. Meanwhile, the median day of PEG prophylaxis after 2020 was day 2 from chemotherapy completion(days 2-3, 108 cases; day 4, 4 cases; and day 5, 1 case)without antibiotic prophylaxis. FN was not observed in any of the cases. The RDI of all regimens was 99.7%. Although there were some differences in chemotherapy regimens, an earlier timing of PEG prophylaxis(especially 24-48 hours from chemotherapy completion)has been shown to reduce the incidence of FN and increase the RDI.