Delaying Filgrastim Administration after Autologous Stem Cell Transplant in Patients with Multiple Myeloma

Given their known clinical benefits, guidelines endorse administration of granulocyte colony stimulating factor (G-CSF) after autologous stem cell transplant (ASCT). However, there is still conflicting data regarding optimal timing of initiation post-transplant and a lack of cost effectiveness analysis. Based on single center studies showing similar results between an early approach and a delayed one, we changed our institutional standard to a delayed initiation strategy in June 2020.

We retrospectively compared the outcomes of multiple myeloma patients post-ASCT given G-CSF either starting on Day+2 (cohort D+2), or on Day+ 5 (cohort D+5), at our institution. Sixteen consecutive patients received G-CSF starting on D+2 from July 2018 to June 2020 and ten patients received G-CSF starting on D+5 since June 2020.

Baseline characteristics were comparable between both cohorts (median age 62 vs 63 years, median CD34+cells 4.01 vs 4.44 x106/kg respectively). The median number of prior treatments, conditioning intensity, disease status at transplant and G-CSF doses were similar in both cohorts. Median ANC at G-CSF initiation was different (3300 in D+2 vs 100 in D+5). The median follow-up for survivors was 337 days for D+5 cohort (range: 151-564 days) vs 738 days for D+2 cohort (range: 571-1071 days). The primary outcome studied was the median time to neutrophil engraftment which was significantly lower in the D+5 cohort vs the D+2 cohort (10 days vs 13 days, p=0.01). Median days from administration of GCSF to hospital discharge were fewer in the D+5 cohort (12 vs 17.5 days, p=0.02). There was no statistically significant difference in the incidence of febrile neutropenia or transfusion requirements with late initiation of G-CSF. Engraftment syndrome and duration of antibiotics were more common in the early cohort, but the difference was not statistically significant. Median length of hospital stay was a day and half shorter in the D+5 cohort (p=0.41). Median OS favored the D+5 cohort (p=0.11) due to higher number of reported transplant related deaths in the D+2 cohort. The average cost savings per patient by implementing the late strategy was $953.70 based on the available purchase price per vial

Late initiation of G-CSF after ASCT in patients with multiple myeloma was associated with a shorter time to neutrophil engraftment and length of stay post transplantation with no difference in overall outcomes. Our cost benefit analysis favored late initiation of G-CSF after ASCT. Based on the ANC nadir, D+5 seems to be the optimal time of initiation of GCSF without compromising any outcomes. Prospective studies using ANC-adapted GCSF administration may provide more definitive information on the subject.