Background: PFG should be administered 24-72 h after CTX, but there is a trend to administer it on the same day as CTX. The aim of our systematic review and meta-analysis (MA) was to compare the outcomes of using PFG on the same day vs day after CTX. Methods: Ten databases were searched. Outcomes included: FN in the CTX cycle 1 and across all cycles, grade IV and grades III/IV CIN, and CTX delays or dose reductions. Random effects MAs were conducted for comparative studies to estimate pooled odds ratios (OR) and 95% confidence interval. We merged comparative studies, using study arms as independent arms, with 1-arm same day studies to estimate pooled weighted rates. As the number of studies varied on outcomes of interest reported, estimates of the pooled weighted rates of these events in same-day vs day-after-CTX should be considered independent of each other. Results: 23 studies on same day PFG (17 with 2 arms, 6 with 1 arm) were retained. Studies varied in outcomes included. Odds (OR, 95%CI) of FN in the CTX cycle 1 (1.48, 1.15-1.90) and across cycles (1.37, 1.02-1.85) were higher for patients (pts) receiving PFG the day of CTX. There was no differential risk of grade IV CIN (1.39, 0.93-2.06), grades III/IV CIN (1.40, 0.71-2.71), CTX delays (0.522, 0.21-1.28) or CTX dose reductions (1.04, 0.32-3.35) between same-day and day-after-CTX pts. Pooled weight rates for both groups were 3.74% vs 2.51% for FN in cycle 1 (n1 = 6, n2 = 6 studies); 2.25% vs 1.79% for FN in any cycle (n1 = 17, n2 = 12); 6.41% vs 3.24% for grade IV CIN (n1 = 7, n2 = 7); 7.04% vs 3.22% for grade III/IV CIN (n1 = 6, n2 = 3); 3.05% vs 1.35% for CTX delays (n1 = 6, n2 = 2); and 1.43% vs 0.434% for CTX dose reductions (n1 = 7, n2 = 2). Conclusions: The rates of FN (cycle 1 and all cycles), CIN/FN grade IV or grades III/IV, CTX delays or CTX dose reductions were nominally low for pts administered PGF same-day and day-after-CTX. Despite these low rates, probabilistically, same-day patients may be at an increased risk of FN, but not of grade IV CIN (primary endpoint in PGF registration trials) and grades III/IV CIN. Same-day PGF pts are at no increased risk of disturbances to their CTX regimen.