Second cancer incidence and cancer mortality among chronic lymphocytic leukaemia patients: a population-based study

Patients with chronic lymphocytic leukaemia (CLL) are known to have increased risks of second cancer. The incidence of second cancers after CLL has not been reported in detail for Australia, a country with particularly high levels of ultraviolet radiation (UVR).

The study cohort comprised of all people diagnosed with a primary CLL between 1983 and 2005 in Australia. Standardised incidence ratios (SIRs) and standardised mortality ratios (SMRs) were calculated using Australian population rates.

Overall, the risk of any second incident cancer was more than double that of the general population (SIR=2.17, 95% confidence interval (CI)=2.07, 2.27) and remained elevated for at least 9 years after CLL. Risks were increased for many cancers, particularly melanoma (SIR=7.74, 95% CI=6.85, 8.72). The risk of melanoma increased at younger ages, but was constant across >9 years of follow-up. Chronic lymphocytic leukaemia patients also had an increased risk of death because of melanoma (SMR=4.79, 95% CI=3.83, 5.90) and non-melanoma skin cancer (NMSC; SMR=17.0, 95% CI=14.4, 19.8), suggesting that these skin cancers may be more aggressive in CLL patients.

We speculate that a shared risk factor, such as general immune suppression, modulated by UVR exposure may explain the increased risk of melanoma and NMSC in CLL patients.