403 - Effect of Non Weight-Based Filgrastim Dosing on Engraftment in Autologous Stem Cell Transplantation

Abstract

Background: The use of granulocyte colony stimulating factor (G-CSF) is currently recommended for use after autologous stem cell transplant by the American Society of Clinical Oncology Clinical Practice Guideline. The rationale behind the use of G-CSF is to decrease duration of neutropenia with the goal of reducing hospital length of stay and risk of infection. Most studies demonstrating a benefit for the use of G-CSF post-autologous stem cell transplant use a dose of 5 mcg/kg/day rounded to nearest vial size. The purpose of this study is to determine whether a flat dose of 300 mcg/day may be used for all patients, regardless of body weight, without affecting time to neutrophil engraftment, which could have implications for costs and resource utilization. Objective: The primary objective of this study was to determine whether there is a difference in time to engraftment, defined as ANC≥500 cells/microL for 3 consecutive days, in patients ≥78 kilograms versus patients <78 kg, using 300 mcg of filgrastim subcutaneously daily for all patients. This weight cutoff was chosen to divide patients into groups that would normally receive 300 mcg or 480 mcg, using a weight-based dose of 5 mcg/kg/day. Secondary objectives were to determine if there is a difference in hospital length of stay or the number of doses of G-CSF administered between the two groups. Methods: A retrospective chart review was conducted of subjects >18 years of age who received an autologous stem cell transplant between June 1, 2013 and May 31, 2016 and received filgrastim 300 mcg/day post-transplant. Data collected included: gender, age, admission weight, indication for transplant, transplant conditioning regimen, date of transplant, stem cell dose, date G-CSF started, number of doses of G-CSF given, time to first day of ANC ≥ 500 cells/microL, time to engraftment, and date of discharge. Results: There were 135 patients in the ≥ 78 kg cohort and 97 subjects in the <78 kg cohort. The median time to engraftment was 14 days (P = .6747, Figure 1) and the median time to first ANC ≥ 500 cells/microL was 12 days (P = .6747) in each cohort. The length of hospitalization was not significantly different (P = .16). The median number of G-CSF doses was 6 regardless of weight. Multivariate regression demonstrated that stem cell dose was the only independent variable associated with time to engraftment. Conclusions: There was no difference in time to engraftment or time to first ANC ≥ 500 cells/microL in patients >78 kilograms versus patients <78 kg using a flat dose of 300 mcg/day of filgrastim, nor was there a difference in median number of G-CSF doses. The total estimated cost savings in this population of 135 patients ≥78 kg, using flat dosing of 300 mcg of filgrastim instead of 480 mcg, was $73,200.