Background: Dose-dense chemotherapy consisting of a combination of epirubicin and cyclophosphamide (EC) improves the survival of patients with breast cancer. Although pegfilgrastim was used at a subcutaneous dose of 6.0 mg in a pivotal study of dose-dense EC treatment, pegfilgrastim at a dose of 3.6 mg has been approved in Japan. We have assessed the feasibility of dose-dense EC treatment supported with a 3.6 mg dose of pegfilgrastim by evaluating the relative dose intensity (RDI) and safety of the treatment, together with measuring the pegfilgrastim concentrations remaining on the day of starting the next cycle of chemotherapy.
Methods: Patients with primary breast cancer received a total of 4 cycles of dose-dense EC treatment every 2 weeks, together with a subcutaneous injection of 3.6 mg pegfilgrastim on the day after chemotherapy. The serum granulocyte colony-stimulating factor (G-CSF) concentrations were measured on the 15th day of every chemotherapy cycle.
Results: From March 2015 through to July 2016, a total of 51 patients (median age 51 years; range 33-73 years) were studied. The mean RDI was 95.2% (range 60.0-100%). Although most adverse events were consistent with those reported in previous studies, pneumocystis pneumonia developed in two patients during the following course of docetaxel treatment. The median serum G-CSF concentration was 92.5 (range 30.4-440) pg/ml.
Conclusions: With support provided by pegfilgrastim injection at a dose of 3.6 mg, dose-dense EC is feasible and associated with maintenance of a high RDI. There was no clinically significant accumulation of serum G-CSF concentrations associated with the use of a 3.6 mg dose of pegfilgrastim at 2-week intervals.
Keywords: Dose-dense EC; Feasibility study; Japan; Pegfilgrastim; Primary breast cancer.