Absolute Lymphocyte Count and CD4 Count Predict a Superior Progression-Free Survival in Non-Hodgkin Lymphoma Patients Treated with Rituximab and Interleukin-12.

The proposed immune-mediated mechanisms of action of Rituximab (ADCC or “vaccinal” effect) suggest that the efficacy of rituximab therapy depends on the immunocompetency of the host. Therapies, such as IL-12, that stimulate the immune system may increase the efficacy of rituximab. Recently, we reported that absolute lymphocyte count (ALC), as a surrogate maker of immune recovery, is a survival prognostic factor in autologous stem cell transplantation for non-Hodgkin’s lymphoma (NHL). We hypothesize host immune competence (i.e, normal ALC counts) would predict a superior survival in NHL patients treated with rituximab-based regimens. The primary end-point of the study was to assess whether the ALC count prior to rituximab therapy predicted progression-free survival (PFS) and the second end-point was to identify which lymphocyte subset was responsible for affecting PFS. We studied 41 NHL patients that participated in our Phase I interleukin-12 plus rituximab study. These patients were selected because the Phase I study required baseline ALC count and flow cytometry analysis providing lymphocyte subset data prior to treatment. There were 20 females and 21 males in the study. The median age of the cohort was 53 years (range: 34–84). PFS was assessed from the initial date of treatment. The median follow-up was 42 months (1–84 months). Patients with an ALC ≥ 0.9 × 10⁹/l experienced a superior PFS versus an ALC < 0.9 × 10⁹/l prior to rituximab therapy (31 months vs 4 months, p < 0.0001). The relapse rate in the ALC ≥ 0.9 × 10⁹/l group was 55% (11/20) versus 95 % (20/21) in the ALC < 0.9 × 10⁹/l (p < 0.0016). Patients with a CD4 count ≥ 500 cells/μl also experienced a superior PFS versus a CD4 count < 500 cells/μl (21 months vs 9 months, p < 0.0062). The relapse rate in the CD4 count ≥ 500 cells/μl group was 56% (9/16) versus 88 % (22/25) in the CD4 count < 500 cells/μl (p < 0.0216). No association with PFS was identified for CD3, CD8, CD19, CD16/56, the use of IL-12, or lymphoma type by WHO classification. CD4 count was found to be an independent prognostic factor for PFS. In the subgroup of patients with follicular lymphoma, patients with an ALC ≥ 0.9 × 10⁹/l experienced a superior PFS versus an ALC < 0.9 × 10⁹/l prior to rituximab therapy (35 months vs 9 months, p < 0.0076). The relapse rate in the ALC ≥ 0.9 × 10⁹/l group was 45% (5/11) versus 90 % (9/10) in the ALC < 0.9 × 10⁹/l (p < 0.0243). Patients with a CD4 count ≥ 500 cells/μl also experienced superior PFS versus a CD4 count < 500 cells/μl (not reached vs 9 months, p < 0.0098). The relapse rate in the CD4 count ≥ 500 cells/μl group was 29% (2/7) versus 86 % (12/14) in the group with a CD4 count < 500 cells/μl (p < 0.0216). CD4 count was found to be an independent prognostic factor for PFS when compared to the Follicular Lymphoma International Prognostic Index at the time of treatment. Our data suggest the significance of an immunocompetent host in predicting the efficacy of rituximab therapy. These data support our previous report that patients with higher number of activated CD4+ cells at the lymphoma site have a better prognosis (