ORIGINAL ABSTRACT

Our understanding of risk factors for the development of chronic lymphocytic leukemia (CLL) is still incomplete and includes genetic and environmental factors. CLL is one of the most familial of all cancers, yet common high-penetrance risk alleles have not been identified. Genome-wide association studies have identified many common variants with low relative risks, whereas exome-wide rare variant analysis has implicated ATM in CLL causation. Environmental factors have also been challenging to identify given the limited understanding of the relevant time period of exposure relative to diagnosis, and the inability to quantify past exposures. Agent Orange and glyphosate herbicides have perhaps the most data to support their role. CLL is preceded by a precursor condition called monoclonal B-cell lymphocytosis (MBL), which could therefore be considered a risk factor, but which itself is likely caused by the same risk factors that ultimately give rise to CLL. Although virtually all people with CLL have a preceding MBL phase, most people with MBL will not develop CLL.