Supplementary Material for: High Risk of Non-Melanoma Skin Cancer in Actinic Keratosis Patients with Skin of Color: A Nationwide Register-Based Cohort Study

Introduction:
Actinic keratoses (AK) are rough, scaly patches from UV exposure, increasing the risk of non-melanoma skin cancer (NMSC). This study examines AK incidence in Korea and its role as a risk factor for NMSC.
Methods:
A retrospective nationwide register-based cohort study analyzed 2,917 AK patients and 14,585 controls from 2002 to 2019. Patients diagnosed with AK were followed until NMSC occurrence, death, emigration, or December 2019.
Results:
AK incidence reached 44.8 per 100,000 person-years in 2019. The adjusted hazard ratio for NMSC in AK patients was 8.91 (95% confidence interval, 5.72-13.90). Higher NMSC risk was observed in female AK patients, those under 60 years, and those with lower income levels. The 16-year cumulative incidence of NMSC was 4.19% in AK patients versus 0.44% in controls.
Conclusion:
AK significantly increases the risk of NMSC in Koreans, highlighting the need for tailored surveillance and treatment strategies.