A Low CD34+ Cell Dose Predicts Relapse and Death Early following Autologous Blood Stem Cell Transplantation

The purpose of this study was to determine if the CD34+ cell dose is independently associated with progression-free (PFS) and overall survival (OAS) for patients treated with autologous blood stem cell transplantation (ASCT). From 1993 to 1999, 277 consecutive patients received ASCT in Calgary for stage 2/3 breast cancer (n = 65), metastatic breast cancer (n = 33), aggressive non-Hodgkin's lymphoma (NHL n = 80), low grade NHL (n = 21), Hodgkin's disease (n = 31), or other cancers (n = 47). Disease status at ASCT was first remission (n = 123), relapse (n = 112), or refractory (n = 42). Patients were grouped into quartiles according to the CD34+ cell dose (<4, 4-7, 7-14, and > 14 × 10(6)/kg). Univariate and multivariate analyses were performed for both PFS and OAS considering the following factors: age, gender, diagnosis, disease status (first remission, relapse, refractory), number of prior chemotherapy regimens, prior radiotherapy (RT), mobilization regimen (G-CSF only, Chemotherapy plus G-CSF, or dose-intensive cyclophosphamide, etoposide, cisplatin (DICEP) plus G-CSF), TBI or non-TBI conditioning, and CD34+ cell dose. The most discriminating cut point of the CD34+ dose for PFS (p <.0001, r(2) =.064) and OAS (p <.0001, r(2) =.066) was found to be 4 × 10(6)/kg. There was no difference in PFS or OAS between the three quartiles above 4 × 10(6)/kg. Using Cox proportional hazards models, factors independently associated with PFS were CD34+ dose < 4 × 10(6)/kg (RR = 2.21, p <.0001), refractory disease status (RR= 6.03, p <.0001), relapsed disease status (RR = 2.04, p =.002), and age > 50 years (RR = 1.91, p =.002). Factors independently associated with OAS were CD34+ dose < 4 × 10(6)/kg (RR = 2.14, p =.0007), refractory disease status (RR = 5.35, p <.0001), relapsed disease status (RR = 2.23, p =.0033), and age > 50 years (RR = 1.81, p =.012). In conclusion, a CD34+ cell dose less than 4 × 10(6)/kg independently predicted lower PFS and OAS rates following ASCT.