Prognostic and Predictive Molecular Biomarkers in Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia (CLL) is a malignancy of B cells with a variable clinical course. Prognostication is important to place patients into different risk categories for guiding decisions on clinical management, to treat or not to treat. Although several clinical, cytogenetic, and molecular parameters have been established, in the past decade, a tremendous understanding of molecular lesions has been obtained with the advent of high-throughput sequencing. Meanwhile, rapid advances in the understanding of the CLL oncogenic pathways have led to the development of small-molecule targeting signal transducers, Bruton tyrosine kinase and phosphatidylinositol 3-kinase, as well as anti-apoptotic protein BCL2 apoptosis regulator. After an initial response to these targeted therapies, some patients develop resistance and experience disease progression. Novel gene mutations have been identified that account for some of the drug resistance mechanisms. This article focuses on the prognostic and predictive molecular biomarkers in CLL relevant to the molecular pathology practice, beginning with a review of well-established prognostic markers that have already been incorporated into major clinical guidelines, which will be followed by a discussion of emerging biomarkers that are expected to impact clinical practice soon in the future. Special emphasis will be put on predictive biomarkers related to newer targeted therapies in hopes that this review will serve as a useful reference for molecular diagnostic professionals, clinicians, as well as laboratory investigators and trainees.