Same-day administration of granulocyte colony-stimulating factors (G-CSFs) following chemotherapy appears to be both safe and effective in managing neutropenia in breast cancer patients, according to recent clinical studies. This approach could significantly simplify treatment protocols while maintaining efficacy in preventing chemotherapy-induced neutropenia.
Eflapegrastim Shows Efficacy in Same-Day Administration
A phase 1 study (NCT04187898) presented at the 42nd Annual Miami Breast Cancer Conference demonstrated that administering eflapegrastim (Rolvedon) on the same day as docetaxel and cyclophosphamide (TC) chemotherapy was effective and safe in patients with early-stage breast cancer.
Among 49 evaluable patients, the mean time to absolute neutrophil count (ANC) recovery in cycle 1 was 1.8 days, with patients experiencing a mean nadir at 1.8 x 10^9/L. The incidence of severe neutropenia was 42.9%, but the mean duration of severe neutropenia was remarkably short at 0.7 days.
"While 43% of patients receiving TC experienced severe neutropenia, the mean duration of severe neutropenia following eflapegrastim [administration] was less than a day and no patients experienced febrile neutropenia–related complications, such as hospitalization or intervention with antibiotics," explained lead study author Dr. Lee Schwartzberg, Chief of Medical Oncology and Hematology for Renown Health–William N. Pennington Cancer Institute.
Only one patient in the study experienced febrile neutropenia, and none reported neutropenic complications requiring antibiotics or hospitalization.
Study Design and Patient Population
The open-label, single-arm phase 1 study was conducted across 13 U.S. sites. Eligible patients were adults with newly diagnosed early-stage breast cancer (stage I to IIIA) suitable for adjuvant or neoadjuvant TC chemotherapy.
Patients received intravenous docetaxel (75 mg/m²) and cyclophosphamide (600 mg/m²) on cycle day 1, followed by a subcutaneous fixed dose of eflapegrastim (13.2 mg) 30 minutes later. This regimen was repeated for cycles 2-4.
The study population (n=53) had a mean age of 62.7 years, with all patients being female. Most patients were White (62.3%), with others being Black (9.4%), Asian (7.5%), or other races (20.8%). Patients had ECOG performance statuses of either 0 (52.8%) or 1 (47.2%).
Safety Profile Consistent with G-CSF Class
Treatment-emergent adverse effects (TEAEs) were experienced by 96.2% of patients, with 88.7% being eflapegrastim-related. The most common musculoskeletal TEAEs were bone pain (52.8%) and back pain (26.4%).
"No new safety concerns were seen, and the eflapegrastim-related AEs were consistent with those observed with other G-CSF products," noted the study authors.
Efbemalenograstim Alfa Shows Similar Promise
In a separate study, the Guard-02 trial (ChiCTR2300078792) presented at the 2025 American Association for Cancer Research Annual Meeting, efbemalenograstim alfa-vuxw (Ryzneuta) administered within 24 hours after chemotherapy also demonstrated efficacy and safety in breast cancer patients.
The incidence of grade 3 or 4 neutropenia across all cycles was 21.62%, with only 2.70% of patients experiencing febrile neutropenia. The overall depth of ANC nadir from cycles 1 to 4 was 2.08 x 10^9/L.
"Administering long-acting G-CSF within 24 hours after chemotherapy was as safe and effective as on day 3 of chemotherapy in reducing [chemotherapy-induced neutropenia] and [febrile neutropenia]," concluded lead investigator Dr. Shoubing Zhou from the Department of Breast Oncology at the First Affiliated Hospital of USTC.
Low Rate of Treatment-Related Adverse Effects
The rate of any-grade treatment-related adverse effects among the 37 patients in the Guard-02 trial was just 13.5%. Two patients experienced low-grade muscle pain, while back pain, fever, and decreased platelet counts occurred in one patient each. Notably, no grade 3/4 treatment-related adverse effects were observed.
Clinical Implications
These findings represent a potential paradigm shift in the administration of G-CSFs following chemotherapy. Traditionally, G-CSFs have been administered 24-72 hours after chemotherapy to avoid potential interference with chemotherapy efficacy. The ability to administer these supportive medications on the same day as chemotherapy could significantly improve patient convenience and potentially enhance treatment adherence.
Dr. Zhou emphasized that "efbemalenograstim alfa provides oncologists an alternative for simplifying the management of [chemotherapy-induced neutropenia] and [febrile neutropenia]."
Background on G-CSF Approval
Eflapegrastim-xnst injection received FDA approval in September 2022 to decrease the incidence of infection caused by febrile neutropenia in patients with non-myeloid malignancies receiving myelosuppressive anticancer drugs. This approval was supported by data from the phase 3 RECOVER and ADVANCE trials, which demonstrated the non-inferiority of eflapegrastim compared to pegfilgrastim (Neulasta).
As research continues, same-day administration of G-CSFs may become a standard approach, potentially reducing clinic visits and improving the overall treatment experience for breast cancer patients undergoing chemotherapy.
