Nationwide population-based cohort study of risk of skin cancer among patients with chroniic lymphocytic leukemia in Denmark

The immunosuppressive treatment of chronic lymphocytic leukemia (CLL) has been suggested to be associated with increased risk of skin cancer. A nationwide population-based cohort study in Denmark investigated the risk of skin cancer and related outcomes among CLL patients compared with control patients without CLL. The study included 8352 patients with a CLL diagnosis between 1990 and 2020, who were matched 1:5 for birth year, sex, geographic regio, educational level, income, marital status, and Charlson Comorbidity Index score with controls (n=41,760). The median age was 70.7 years (IQR 62.2-78.3); 58.7% were male. The absolute 10-year risk of skin cancer among the CLL patients was 13.5% (95% CI 12.7-14.3), compared with 6.9% (6.6-7.2) among the controls (p<0.001). CLL patients had an increased risk of most skin cancer subtypes, with the most common being basal cell carcinoma (8.6%). CLL patients, compared with controls, had a higher risk of both skin cancer metastasis (0.7% versus 0.1%) and skin cancer-specific death (0.3% versus 0.1%). The authors conclude that CLL patients have an increased risk of developing skin cancer and related adverse outcomes.