Increased Prevalence of Left-sided Skin Cancer: A Systematic Review and Meta-analysis

Abstract

Background: Based on trends demonstrated in the United States, a very insignificant number of people have shown a predisposition to left-sided skin cancer. However, to date, no systematic review or meta-analysis has demonstrated the predominance of left-sided skin cancers over right- sided skin malignancies. Objective: We systematically reviewed and meta-analyzed all data pertaining to locations of skin cancers. Methods: All data were pooled using the Mantel-Haenszel method (random-effects weighting); an inverse variance model featuring fixed-effects weighting was applied to explore the robustness of modeling. Heterogeneity was evaluated using the I2 test. Dichotomous outcomes with respect to the prevalence of left- and right-sided skin cancers are presented as relative risks (RRs) with 95% confidence intervals (CIs). Results: Nine studies were included in our evaluation. Our study sample included: 182,840 patients with malignant melanoma (MM), 1,419 patients with basal cell carcinoma (BCC), and 331 patients with squamous cell carcinoma (SCC). Meta-analyses of pooled observational data revealed greater prevalence of left-sided MM compared to right-sided MM (RR 0.91, 95% CI 0.89∼0.92, p＜0.01), while left-sided SCC was more prevalent than right-sided SCC (RR 0.83, 95% CI 0.71∼0.97, p=0.02). However, right-sided BCC was more prevalent than left-sided BCC (RR 1.07, 95% CI 0.95∼1.19, p=0.26). Conclusion: Observational studies vary greatly in terms of design, methodological quality, and types of patients studied. Of note, only a few studies analyzing BCC and SCC were included in our present meta-analysis. Additionally, a selection and reporting bias could have affected our results. Our meta-analysis suggests that both MM and SCC demonstrate a left-side bias, but BCC does not.