Worldwide, there are ~191,000 cases and 61,000 deaths per year due to chronic lymphocytic leukaemia (CLL) (Global Burden of Disease Cancer Collaboration, 2017). It is the most common form of adult leukaemia in the Western world (Gibson et al., 2013; Hallek, 2017). In the UK, CLL accounts for 1% of all new cancer cases and 38% of all leukaemias (CRUK, 2014).

Estimates of age-adjusted CLL incidence rates range from 3.7 to 4.5 per 100,000 people in the UK, USA and Australia (Gibson et al., 2013; CRUK, 2014; Ruchlemer et al., 2015). The Haematological Malignancy Research Network (HMRN) reports an annual crude rate in the UK of 6.4 per 100,000 people (between 2004-2009) and a European age-standardised rate of 5.0 per 100,000 (Smith et al., 2011). Age standardised rates for the European population tend to be lower than actual rates due to the fact that this hypothetical standard has a younger age structure (Smith et al., 2011).

UK and European incidence rates have increased by around 85% since the 1970s but have stabilised in recent years (CRUK, 2014). It has been noted that these increased rates may be in part due to changes in diagnosis, classification and registration of leukaemia (CRUK, 2014). Largest increases were seen in the 60–69 age group with European incidence rates doubling since the mid 1970s but becoming stable from 2000 onwards (CRUK, 2014).