Infused Autograft Absolute Lymphocyte Count Predicts Superior Survival in Diffuse Large B Cell Lymphoma Patients Post-Autologous Peripheral Blood Hematopoietic Stem Cell Transplantation: A Matched Case-Control Study

Abstract

Our group published a double phase III trial showing that patients infused with an autograft absolute lymphocyte count (A-ALC) ≥0.5×109 cells/kg experienced superior survival post-autologous peripheral blood hematopoietic stem cell transplantation (APBHSCT). Based on the results from our phase III study, as well as published retrospective studies, on April 1, 2017, our Bone Marrow Transplant Program changed our standard practice to collect an A-ALC ≥0.5×109 cells/kg in addition to stem cells for lymphoma patients undergoing APBHSCT. The primary objective of the present study was to continue to assess the prognostic ability of A-ALC by evaluating overall survival (OS) and progression-free survival (PFS) of diffuse large B cell lymphoma (DLBCL) patients who underwent APBHSCT after April 1, 2017, compared with matched control groups at a 1:1:1 ratio with DLBCL patients infused with an A-ALC <0.5×109 cells/kg and A-ALC ≥0.5×109 cells/kg before April 1, 2017. Using the GREEDY algorithm, 85 DLBCL patients (cases) infused with an A-ALC ≥0.5×109 cells/kg after April 1, 2017, were matched at a 1:1:1 ratio with control groups of DLBCL patients who underwent transplantation before April 1, 2017: patients infused with an A-ALC <0.5×109 cells/kg (control 1) and patients infused with an A-ALC ≥0.5×109 cells/kg (control 2) before April 1, 2017. Groups were matched in terms of sex, age, stage, lactate dehydrogenase (LDH) level, performance status, extranodal disease, International Prognostic Index (IPI), and disease status before APBHSCT (complete or partial response). Survival follow-up was truncated at 3 years from the date of transplantation. Cases, control 1, and control 2 were balanced as to age (P=.8), sex (P=.9), LDH (P=.6), performance status (P=.5), extranodal disease (P=.2), IPI (P=.6), and disease status before APBHSCT (P=.2). Cases and control 2 showed superior OS and PFS compared with control 1. Multivariate analysis including all patients continued to show A-ALC ≥0.5×109 cells/kg as an independent predictor for OS (hazard ratio [HR], 0.382; 95% confidence interval [CI], 0.241 to 0.605; P < .0001) and PFS (HR, 0.437; 95% CI, 0.279 to 0.629; P < .0001). Our matched case-control study supports the results of previously published retrospective studies and our phase III study showing that the infusion of A-ALC is a prognostic factor for survival in DLBCL patients undergoing APBHSCT. Our findings support the practice of collecting not only enough stem cells for hematologic engraftment, but also enough immune effector cells (ie, A-ALC) to improve clinical outcomes in DLBCL patients post-APBHSCT.