Half Dose Pegfilgrastim for Patients With Breast Cancer During Chemotherapy: A Case-series.

Background/aim: This study aimed to show the trend of neutrophil counts and frequency of febrile neutropenia after changing pegfilgrastim from 3.6 mg to 1.8 mg.

Patients And Methods: This case-series study was performed between April 2016 and December 2021 at Hyogo Prefectural Amagasaki General Medical Center. All patients who reduced their normal dose of 3.6 mg pegfilgrastim to 1.8 mg due to adverse events or markedly elevated neutrophil counts were included. Any type of chemotherapy was acceptable. Patients who dropped out within 1 month of receiving 1.8 mg pegfilgrastim were excluded. The primary outcome was the neutrophil counts after receiving 1.8 mg pegfilgrastim. The secondary outcome was febrile neutropenia, which was evaluated by the Common Terminology Criteria for Adverse Events v5.0.

Results: The study included seven patients who used a regimen of dose-dense epirubicin and cyclophosphamide, trastuzumab, pertuzumab, and docetaxel, docetaxel, or docetaxel and cyclophosphamide. After using 1.8 mg pegfilgrastim, neutrophil counts changed from a mean of 18,944 [standard deviation (SD)=-7,768] to only 4,447 (SD=1,224). The patients experienced grades 1 to 3 adverse events during the use of 1.8 mg and 3.6 mg pegfilgrastim doses, including febrile neutropenia, and pain. Four patients (57%) complained of grade 1 or 2 fatigue and anorexia. After switching from 3.6 mg pegfilgrastim to 1.8 mg, three patients (42%) experienced adverse events.

Conclusion: In patients who experienced adverse events due to markedly elevated neutrophil counts with pegfilgrastim, reducing the dose of pegfilgrastim by half may reduce adverse events.