Absolute lymphocyte count predicts therapeutic efficacy of rituximab therapy in follicular lymphomas

The immunologic mechanisms of action of rituximab include complement mediated lysis and antibody-dependent cellular cytotoxicity. We hypothesised that a stronger host immune system prior to rituximab therapy for follicular (grades 1and 2) lymphomas (FL) would result in better response rates and longer time to progression (TTP). Thus, we studied the role of absolute lymphocyte count (ALC) prior to rituximab therapy on treatment efficacy and TTP in FL patients. Between 1996 and 2002, 79 FL patients were treated with single agent rituximab during their lymphoma treatment at the Mayo Clinic. The median age of the cohort was 56.6 years (range: 25-98 years). The median TTP was 12.5 months (range: 1-76 months). Superior TTP was observed with an ALC > or =0.89 x 10(9)/l (n = 40) compared with an ALC <0.89 x 10(9)/l (n = 39) at the time of rituximab therapy (median: 36.5 vs. 8.1 months, respectively, P < 0.0009). Higher complete response rates were observed in the ALC > or =0.89 x 10(9)/l (23/40, 58%) compared with the ALC <0.89 x 10(9)/l (5/39, 13%) (P < 0.0001). Multivariate analysis showed ALC to be an independent predictor for TTP. This study supports our hypothesis that a higher ALC predicts longer TTP following rituximab therapy.