Background and purpose:Administration of pegylated granulocyte-colony-stimulating factor (peg-GCSF) 24 to 72 hours after chemotherapy is usually recommended. Next-day administration (after 24 hours) resulted in fewer duration of grade (Gr) 4 chemotherapy-induced neutropenia (CIN) and decreased severity of CIN than same-day (within 4 hours). However, patients sometimes receive same-day Peg-GCSF for the sake of convenience. In addition, a few prior studies showed that the same-day method is comparable or superior to the next-day method in preventing CIN, especially in chemotherapy regimens that include day 1 myelosuppressive agents. Thus, we aim to verify the hypothesis that same-day administration of pegteograstim, a new formulation of peg-GCSF, is non-inferior to next-day administration in terms of Gr4 CIN duration.Methods:This study is a randomized, multicenter, open-label, investigator-initiated phase 3 study. Patients with adjuvant/neoadjuvant or first-line palliative chemotherapy comprising intensively myelosuppressive agents on day 1 (mFOLFIRINOX, ECb, EP, FOLFIRI, and FOLFOX) are enrolled. The patients are assigned to the same-day arm or the next-day arm in a 1:1 ratio. The randomizations are stratified according to number of patient CIN risk factors (1 vs ≥2), chemotherapy setting (perioperative vs palliative), and interval (2-week vs 3-week). In the same-day arm, pegteograstim 6 mg is subcutaneously injected within 4 hours after completion of chemotherapy. In the next-day arm, pegetograstim is injected at 24 to 36 hours post-chemotherapy. A complete blood count test is performed daily from day 5 to 9 during the cycle 1. The primary endpoint is duration of Gr4 CIN (cycle 1), and secondary endpoints include incidence of Gr 3 to 4 CIN (cycle 1), severity of CIN (cycle 1), time to recovery absolute neutrophil count 1000/μL (cycle 1), incidence of febrile neutropenia, incidence of CIN-related dose delay, and dose intensity. In order to verify non-inferiority of 0.6 days, we estimated a significance level of 5%, power of 80%, and drop-out rate of 15%. This results in the need for a total of 160 patients, 80 in each group.