Factors Associated with Absolute Neutrophil Count Dynamics and Docetaxel-Adryamicin-Cyclophosphamide (TAC) Chemotherapy Induced Neutropenia During Extended Filgrastim Administration in Breast Cancer Patients

Background: Myelosuppressive effects of chemotherapy for breast cancer treatment may trigger chemotherapy-induced neutropenia (CIN) and febrile neutropenia (FN). Filgrastim has been widely used as prophylaxis against CIN and FN. However despite filgrastim administration, some study showed FN still occur and cause patient vulnerability to infection. This study aims to evaluate factors associated with Absolute Neutrophil Count (ANC) dynamics and Docetaxel-Adryamicin-Cyclophosphamide (TAC) CIN during extended filgrastim administration in breast cancer patients. Methods: Patients were selected among breast cancer in-patients who fulfilled the eligibility criteria. Patient characteristics data and ANC were collected. The entire patients received 5μg/kg/day filgrastim by subcutaneous injection 24 hours post-chemotherapy. ANC was monitored daily and filgrastim administration was stopped when ANC reached >10000/mm³ or 14 days of administration. Kruskall-Wallis test and Spearman Correlation test was performed to analyze ANC dynamics and CIN-related factors. Results: This study included 42 breast cancer patients. Patient age median was 52 (31-70) years old. ANC nadir could be observed around 5-7 days after chemotherapy and FN occurred in two out of 38 grade 4 neutropenia patients (4.8%). Critical ANC lasted for 1 day, 2 days, and 3 days respectively in 9 (23.7%), 25 (65.8%) and 4 (10.5%) patients. There was no correlation between neutropenia and age. ANC slope and recovery duration did not show a significant difference. However, depth of nadir is inversely correlated with the duration of ANC recovery (>10000/mm³) and the duration during the peak on the 2^nd day until reaching nadir both with fair strength, r = −0.489 and r = −0.438 (p <0.05), respectively. No sepsis incidence had manifested. Conclusion: CIN still occurred in breast cancer patient receiving filgrastim primary prophylaxis regardless of age and neutropenia severity. Nadir as the lowest point of ANC should be noted as a pivotal milestone for ANC slope and recovery evaluation.