A Comparison of Flow Cytometry Detection of Minimal Residual Disease and Chimerism Kinetics in Chronic Lymphocytic Leukemia Patients After Allogeneic Hematopoietic Stem Cell Transplantation (Report‪)‬

1. INTRODUCTION Important advances have been made over the past two decades in the prognosis and treatment of chronic lymphocytic leukemia (CLL) [1]. New therapeutic approaches aim to induce molecular remission. The better quality of response, provided by novel agents and new therapeutic approaches, requires necessarily more sensitive tools for precise remission assessment [2-7]. The evaluation of response to treatment in CLL is currently based on the National Cancer Institute (NCI) criteria [8]. Several studies have demonstrated that CLL patients achieving response at a molecular level without any detectable minimal residual disease (MRD) have a longer survival [5-9]. Using a very high sensitive flow cytometry technique, several groups have shown that patients in complete remission (CR) with detectable MRD have an increased risk of early relapse [3,6]. In this setting, bone marrow biopsy appeared to be less sensitive than flow cytometry [10]. Conversely, similar results have been shown with real-time quantitative (RTQ) polymerase chain reaction (PCR) and MRD flow monitoring in terms of leukemia cell clearance kinetics and timing for reaching MRD negativity [6].