Low CD34+ Cell Doses Are Associated with Increased Cost and Worse Outcome after Tandem Autologous Stem Cell Transplantation in Patients with Relapsed or Refractory Germ Cell Tumors

Abstract

Tandem autologous stem cell transplantation (ASCT) improves long-term survival of platinum-refractory germ cell tumors (GCT) patients. Studies, predominantly in lymphoma, showed that CD34⁺ cell doses > 5.0 × 10⁶/kg/single transplant led to decreased resource utilization. Because most GCT patients have received prior cisplatin-based treatment, collecting >10 × 10⁶ CD34⁺ cells/kg is challenging. We analyzed the effect of CD34⁺ cell dose on resource utilization and outcome in 131 GCT patients, median age 29.5 years (range, 16 to 58), undergoing tandem ASCT. Of 262 individual transplants performed, 120 were performed as inpatient and 142 as planned outpatient. Overall, median CD34⁺ dose per transplant was 3.1 × 10⁶/kg (range, 0.8 to 16.0), with no significant difference between inpatient and outpatient transplants. Patients were divided into quartiles based on the CD34 cell dose infused: Q1, 0.8 to 1.9 × 10⁶/kg; Q2, 2.0 to 2.9 × 10⁶/kg; Q3, 3.0 to 4.1 × 10⁶/kg; and Q4, 4.2 to 16.0 × 10⁶/kg. For all patients higher CD34⁺ cell doses were associated with significantly shorter times to neutrophil (P <.001) and platelet recovery (P <.001). For inpatient transplants higher CD34⁺ doses were significantly associated with shorter length of hospital stay (P <.001), fewer days of filgrastim (P <.001), i.v. antibiotic (P = .012) and antifungal (P = .03) usage; and fewer RBC (P = .001) and platelet units transfused (P <.001), resulting in overall lower cost of care (P < .001). Of the 142 planned outpatient transplants, 100 admissions were required for a median length of hospital stay of 7.0 days (range, 1 to 18). Although there was no significant difference in the rates of hospitalization between patients in different CD34⁺ cell dose quartiles, a significant trend was observed for shorter hospitalization (P = .01) and fewer RBC (P = .002) and platelet (P = .005) transfusions with higher CD34⁺ cell dose quartile. Patients receiving CD34⁺ cell doses in the lowest dose quartile (Q1) had significantly worse progression-free survival and overall survival compared with patients receiving higher CD34⁺ cell doses. Overall, resource utilization, including cost of care, is significantly reduced when patients receive higher CD34⁺ cell doses, indicating greater efforts to improve peripheral blood stem cell collection in this population are needed.

Keywords: CD34(+) cells; Germ cell tumors; Mobilization; Resource utilization; Stem cell transplantation.