Assessment of Chronic Lymphocytic Leukemia and Small Lymphocytic Lymphoma by Absolute Lymphocyte Counts in 2,126 Patients: 20 Years of Experience at The University of Texas M.D. Anderson Cancer Center

Abstract

Purpose Chronic lymphocytic leukemia (CLL) and small lymphocytic lymphoma (SLL) are currently considered the same entity, but controversy remains over whether CLL and SLL should be treated similarly. We assessed whether characteristics of patients with CLL and SLL differ in ways other than the absolute lymphocyte count (ALC) and evaluated treatment outcomes and prognostic factors. Methods We searched the electronic database for patients with CLL or SLL who presented to The University of Texas M.D. Anderson Cancer Center (Houston, TX) between 1985 and 2005. We reviewed patient records to determine presenting characteristics, treatment, and clinical outcomes. Cox models using training and validation sets of patients and resampling methods were used to develop a model predicting survival. Results Among 2,126 consecutive CLL/SLL patients, 312 (15%) had ALC less than 5 × 109/L. Patients with ALC less than 5 × 109/L had lower rates of cytogenetic abnormalities (P = .0002) and higher rates of CD38-positive results (P = .0002) and had mutated immunoglobulin heavy-chain variable region gene status (P = .034). Rates of response, survival, and failure-free survival (FFS) were not different among ALC groups. Regimens that included rituximab and a nucleoside analog were associated with superior rates of response and FFS compared with other therapies, irrespective of ALC. Deletion 17p or 6q with or without other cytogenetic abnormalities, age at least 60 years, β2-microglobulin at least 2 mg/L, albumin less than 3.5 g/dL, and creatinine at least 1.6 mg/dL were each found to independently predict shorter survival and formed the basis of a scoring system. Conclusion Patients with CLL or SLL can be treated similarly. A new prognostic score is proposed.