Second primary malignancies in Asian chronic lymphocytic leukaemia patients: A Taiwan Cancer Registry Study.

While second primary malignancies (SPMs) in Western patients with chronic lymphocytic leukaemia (CLL) are well documented, data from Asian populations remain limited. This nationwide, retrospective cohort study assessed SPM risk in 2702 CLL patients diagnosed in Taiwan between 1991 and 2020 using the Taiwan Cancer Registry. Standardized incidence ratios (SIRs), absolute excess risks and cumulative incidences were calculated relative to the general population, stratified by sex, age, latency and treatment. The overall SPM risk was elevated (SIR, 1.14, 95% confidence interval [CI], 1.00-1.29), with a 5-year cumulative incidence of 6.53%. Notably increased risks were observed for epithelial skin cancer (SIR, 2.55; 95% CI, 1.60-3.86) and urinary bladder cancer (SIR, 1.99; 95% CI, 1.06-3.41). A lower risk of breast cancer was detected among younger women (SIR, 0.29; 95% CI, 0.06-0.85). SPM risk was highest within 5 years of CLL diagnosis (SIR, 2.72; 95% CI, 2.27-3.22) and then decreased thereafter (SIR, 0.67; 95% CI, 0.56-0.81). These findings reveal a distinct SPM risk profile among Asian CLL patients, particularly the excess risk of bladder cancer, underscoring the importance of tailored surveillance strategies for this population.