Chronic Lymphocytic Leukaemia (CLL) is the most common leukaemia in Australia with an age-standardised rate of 4.6 per 100,000, and is twice as common in males than females (6.3 vs 3.0 per 100,000 respectively). There have been significant improvements in our knowledge of CLL biology, especially the genetic and other factors leading to its highly heterogeneous clinical course. Flow cytometry remains pivotal to the identification of a CLL clone as the primary means of diagnosis. Small clones, Monoclonal B-Lymphocytosis (MBL), are usually identified in the flow cytometry laboratory, though the reporting, definition and differentiation between CLL, MBL and SLL remains a point of confusion for many patients, clinicians and even the medical literature, with subtle discrepancies between published definitions.

The achievement of minimal residual disease (MRD) negativity following immunochemotherapy is an important prognostic factor and the monitoring of MRD can be very useful to assess individual patients. The revised ERIC flow cytometric methodology enables high sensitivity evaluation of MRD. While MRD status is not currently a treatment end-point, there are a number of clinical trials in progress including the Australasian Leukaemia and Lymphoma Group (ALLG) CLL6 study evaluating this issue.

There have been major advances in treatment over the last few years. These include the inhibitors of the B-cell receptor signal pathway, particularly of Bruton Tyrosine Kinase (Btk) such as ibrutinib, inhibitors of PI3Kinase such as idelalisib, and the bcl2 inhibitor venetoclax. These drugs are having a major beneficial effect for patients, particularly those with relapsed and refractory disease.