The cause of CLL is unknown, and there are currently no effective prevention strategies.

The risk factors for developing CLL include:

• older age – 83 per cent of all people diagnosed with CLL are 60 years of age or older (AIHW 2021)
• sex – CLL is more common in males than females (AIHW 2021)
• family history – people with a first-degree relative (parent, sibling or child) with CLL or other lymphoproliferative disorder have a six- to nine-fold increased risk of developing CLL (Eichhorst et al. 2021), but the underlying genetic cause is unclear and there is no available screening test for genetic predisposition
• race/ethnicity – CLL is more common in Caucasians and less common in people of Asian descent (including South Asian, East Asian and Southeast Asian) (Kawamata et 2013; Miranda-Filho

et al. 2018; Wu et al. 2010; Yang et al. 2021).

Exposure to chemicals such as Agent Orange, a herbicide used in the Vietnam War, is associated with developing lymphoproliferative disorders generally. Any potential causative link to CLL specifically has not been definitively established, and research is ongoing (Chang et al. 2015; DVA 2020; Frumkin 2003; McBride et al. 2013; Mescher et al. 2018).

While there is no evidence linking lifestyle changes to reduced risk of CLL, it is important to encourage people to reduce modifiable risk factors for other types of cancer and health conditions. This includes providing advice on regular screening, skin checks, sun-safe behaviours (Kleinstern et al. 2016; 2020), preventing or reducing obesity, and support to quit smoking.

This is particularly important since people with CLL have an increased risk of developing other cancers including lung and upper aerodigestive cancers such as pharyngeal and oesophageal cancer, as well as skin cancers.

CLL is usually slow growing, and in most cases it is picked up early during routine blood tests for unrelated conditions. There is currently no established benefit from early detection.