Higher Infused Lymphocyte Dose Predicts Higher Lymphocyte Recovery, Which in Turn, Predicts Superior Overall Survival following Autologous Hematopoietic Stem Cell Transplantation for Multiple Myeloma

Autologous stem cell transplantation (ASCT) is the standard of care for patients with multiple myeloma (MM) younger than 70 years. However, despite this aggressive therapy most patients will still die of progressive disease. Recent reports have suggested that lymphocyte recovery is an important predictor of relapse or progressive disease in a number of hematologic malignancies including MM. We have conducted retrospective analysis of factors that could predict overall (OS) and progression free survival (PFS) in patients with MM who had ASCT. One hundred nineteen patients with multiple myeloma underwent ASCT. The median OS and PFS were 64 and 32 months, respectively. Univariate and multivariate analysis using Cox proportional hazards regression model showed that absolute lymphocyte count on day 30 following ASCT (ALC-30), international staging system (ISS) stage at diagnosis, and age at diagnosis significantly influenced OS and PFS following ASCT. OS (96 versus 48 months, P = .04) and PFS (43 versus 29 months, P = .03) following ASCT were higher in patients with ALC-30 ≥1.0 × 109/L compared to patients ALC-30 <1.0 × 109/L. Higher ALC-60, ALC-100, ALC-180, and ALC-365 did not predict superior OS and PFS. Patients with early-stage disease had significantly higher OS (ISS stages I, II, and III: 96, 53, and 29 months, respectively; P = .0023) and PFS (ISS stages I, II, and III: 55.5, 31, and 12 months, respectively; P = .027) compared to patients with advanced-stage disease at diagnosis. On univariate analysis, the type of initial chemotherapy (melphalan, VAD, PCAB), lymphocyte count on day of leukapheresis, and the lymphocyte dose infused (LY-DO) significantly influenced lymphocyte recovery following ASCT. Patients who received higher lymphocyte dose (LY-DO) ≥0.2 × 109/kg had higher median ALC-15 (0.25 versus 0.19 × 109/L; P = .3), ALC-30 (1.20 versus 0.99 × 109/L; P = .08), ALC-60 (1.90 versus 1.01 × 109/L; P = .013), ALC-100 (1.58 versus 1.03 × 109/L; P = .016), and ALC-180 (1.33 versus 1.01 × 109/L; P = .1), compared to patients who received LY-DO <0.2 × 109/kg. In summary, our data suggest that infusing large numbers of lymphocytes improves lymphocyte recovery post-ASCT, and that higher ALC-30 is associated with better PFS and OS. These data suggest that a threshold number of CD34+ cells should not be the only parameter considered for an adequate PBSC collection—perhaps a certain number of lymphocytes should be aimed for as well.