History of Blistering Sunburns and Keratinocyte Carcinoma Risk in a Nationwide US Cohort

Abstract Background: The large and growing burden of keratinocyte carcinoma (KC), including basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), suggests a need to identify high-risk individuals. We examined the association between KC risk and history of blistering sunburns in childhood and adulthood and investigated whether sun sensitivity modifies these associations. Methods: Data were obtained from the large, nationwide US Radiologic Technologists cohort, with baseline sunburn history and sun sensitivity traits collected via self-administered questionnaires. Participants were followed until diagnosis of first primary cancer or completion of a follow-up questionnaire (2003–2014). Hazard ratios (HR) and 95% confidence intervals (95% CI) were estimated using Cox proportional hazards models. Results: Among 40,204 participants, those reporting ever blistering sunburn had higher risk of BCC (HR = 1.37; 95% CI, 1.26–1.49) and SCC (HR = 1.41; 95% CI, 1.19–1.66). The HRs of BCC per blistering sunburn in childhood and adulthood were 1.06 (95% CI, 1.05–1.07) and 1.05 (95% CI, 1.04–1.06), respectively. The HRs for SCC were 1.08 (95% CI, 1.06–1.11) and 1.07 (95% CI, 1.05–1.09) per blistering sunburn in childhood and adulthood, respectively. Most sun sensitivity factors and other measures of ultraviolet radiation (UVR) exposure did not significantly modify these associations. Conclusions: The number of blistering sunburns was associated with increased KC risk independently of an individual’s pigmentary features and ambient UVR. The associations were similar for childhood and adulthood sunburns. Impact: History of blistering sunburn is an important risk factor for KC, even among groups that might otherwise be overlooked because of their overall lower risk of KC, such as individuals who have darker pigmentary features or those residing in locations with less ambient UVR.