Outcomes of chemotherapy-induced (febrile) neutropenia prophylaxis with biosimilar filgrastim (Zarzio®) initiated "same-day" (< 24 h), "per-guidelines" (24-72 h), and "late" (> 72 h): findings from the MONITOR-GCSF study.

Purpose: Granulocyte colony-stimulating factors (G-CSFs) are indicated for prophylaxis or management of chemotherapy-induced neutropenia (CIN) and febrile neutropenia (FN). Guidelines recommend G-CSF 24-72 h following chemotherapy; however, some evidence suggests that G-CSF initiated < 24 h may benefit some patients.

Methods: MONITOR-GCSF was a prospective, observational, multicenter, pan-European study of 1447 chemotherapy-treated patients receiving daily biosimilar (standard) filgrastim (Zarzio®/Zarxio®, filgrastim-sndz, Hexal AG, Sandoz Inc.). In this analysis, cycles were classified as same-day, per-guidelines, or late if G-CSF support was initiated < 24 h, 24-72 h, and > 72 h after chemotherapy. Outcomes included occurrence of CIN of any grade (CIN1/4), grade 3 or 4 (CIN3/4), grade 4 (CIN4), or FN: CIN/FN-related hospitalization or CIN/FN-related chemotherapy disturbance.

Results: A total of 5930 chemotherapy cycles from 1423 evaluable patients from MONITOR-GCSF had data for day of G-CSF initiation: 795 cycles (13.4%) classified as same-day, 3320 (56.0%) as per-guidelines, and 1815 (30.6%) as late. Groups did not differ as to CIN1/4 and FN episodes, or CIN/FN-related hospitalizations or chemotherapy disturbances. Patients in the same-day and per-guidelines groups had statistically similar odds of not experiencing any outcomes of interest in any given cycle. Patients in the late group had worse odds of experiencing CIN1/4, CIN3/4, and CIN4 episodes in any given cycle. Proportions of patients reporting clinical events of interest were generally similar.

Conclusions: This real-world evidence indicates that CIN/FN prophylaxis initiated with biosimilar filgrastim within 24-72 h post-chemotherapy is effective and safe. Filgrastim administration on the day of chemotherapy may be appropriate in some patients.