Efficacy of reduced dose of pegfilgrastim in Japanese breast cancer patients receiving dose-dense doxorubicin and cyclophosphamide therapy

This retrospective study aimed to evaluate the efficacy of a 3.6-mg dose of pegfilgrastim for primary prophylaxis in Japanese breast cancer patients receiving dose-dense chemotherapy. Patients treated with adjuvant or neoadjuvant chemotherapy for early-stage breast cancer at the Tokyo-West Tokushukai Hospital were included in this analysis. Because 6 mg pegfilgrastim has not yet been approved for use in Japan, we compared the outcomes of a dose-dense doxorubicin and cyclophosphamide regimen plus 3.6 mg pegfilgrastim support with a conventional dose epirubicin and cyclophosphamide regimen. The incidence of febrile neutropenia, relative dose intensity, dose delay, dose reduction, regimen change and hospitalization because of neutropenia were assessed. From November 2013 to March 2016, 97 patients with stage I-III invasive breast cancer were analyzed (dose-dense doxorubicin and cyclophosphamide plus 3.6-mg pegfilgrastim group, n = 41; epirubicin and cyclophosphamide group, n = 56; median ages, 49.0 and 48.5 years, respectively). Febrile neutropenia occurred during the first chemotherapy cycle in 7 of 56 patients (12.5%) in the epirubicin and cyclophosphamide group and 0 of 41 patients in the dose-dense doxorubicin and cyclophosphamide group (P = 0.02). The average relative dose intensities were 97.9% and 96.8%, respectively (P = 0.28), with corresponding dose delay rates of 4.9% (2/41) and 16.1% (9/56), respectively (P = 0.11) and dose reduction rates of 0% (0/41) and 7.1% (4/56), respectively (P = 0.16). Our results indicate the efficacy of a 3.6-mg pegfilgrastim dose for the primary prevention of febrile neutropenia in dose-dense doxorubicin- and cyclophosphamide-treated Japanese breast cancer patients.