Evaluating the causality between skin tanning, radiated disorders, and basal cell carcinoma: a multivariable Mendelian randomization analysis

The causality of ease of skin tanning and radiation-related disorders of the skin and subcutaneous tissue with basal cell carcinoma (BCC) remains unclear. Our objective was to investigate whether ease of skin tanning and radiation-related disorders of the skin and subcutaneous tissue have a relation with the occurrence and development of BCCs. In this work, independent genetic variants strongly associated ( P < 5e−08) with ease of skin tanning and radiation-related disorders of the skin and subcutaneous tissue were selected as instrumental variables from corresponding genome-wide association studies (GWASs). Summary-level data for BCC was obtained from the European Bioinformatics Institute (EBI). Two-sample univariable and multivariable Mendelian randomization (MR) were performed. Sensitivity analyses were preformed via MR-Egger regression, heterogeneity test, pleiotropy test, and leave-one-out sensitivity test. We observed positive causal effect both for ease of skin tanning [odds ratio (OR) = 2.102, 95% confidence interval (CI) = 1.915–2.306, P = 2.71e−55] and radiation-related disorders of the skin and subcutaneous (OR = 1.603, 95% CI = 1.483–1.734, P = 3.41e−32) on occurrence of BCCs based on univariable MR analyses. In the multivariable mendelian randomization (MVMR) analysis of BCC risk, we also observed a direct causal effect of ease of skin tanning (ORMVMR = 1.623, 95% CI = 1.445–1.824, PMVMR =3.41e−16) and radiation-related disorders of the skin and subcutaneous (ORMVMR = 1.208, 95% CI = 1.107–1.319, PMVMR = 2.46e−05) on BCCs. The findings suggest that the high risk of BCCs can be attributed to ease of skin tanning and radiation-related disorders of the skin and subcutaneous tissue.