Introduction: Noninterventional study (NIS) on application and effectiveness of primary G-CSF prophylaxis with lipegfilgrastim in primary breast cancer patients undergoing dose-dense (dd) or intense-dose-dense (idd) chemotherapy (CTx) regimen in daily clinical practice. Methods: Prospective, multicenter, single-arm, NIS in 41 private practices and 27 hospitals in Germany. Results: Data analysis of 282 patients with a mean age of 49 years (93.6% of patients <65 years) was performed. Hormone receptor status was triple negative in 29.8% of patients, and 81.9% of patients were HER2 negative. A total of 73.8% of patients received "EC dd -> taxane CTx." Patients received lipegfilgrastim prophylaxis in 97.5% of 1,121 documented dd/idd cycles. Overall, the study registered 275 events of SN (CTCAE grade 3 or 4) and 9 events of FN. During the first dd cycle, SN occurred in 33.3% and FN in 1.1% of patients. CTx delay or dose reduction due to neutropenia was required in 2.5% of patients during the 4 dd cycles with lipegfilgrastim support. Overall, 314 adverse events (AEs) were reported from 107 patients and 27 serious AEs from 21 patients. None of the SAEs was "fatal," and CTCAE grade was mostly (89.6%) assessed as "1" or "2." According to the treating physicians, 99.3% of all patients benefitted from lipegfilgrastim prophylaxis, and tolerability was mostly rated "very good" or "good." Conclusion: These results suggest that primary lipegfilgrastim prophylaxis is effective and safe in clinical routine and is beneficial in primary breast cancer patients undergoing dd/idd-ETC CTx.
