The Influence of Sun Exposure, Melanocytic Nevi, and Phenotypic Factors on the Development of Cutaneous Melanoma: A Case-Control Study from Lithuania

Abstract

Introduction and Objectives: We conducted a case-control study in Lithuania to elucidate risk factors of cutaneous melanoma (CM).Materials and methods: This study analyzed 180 subjects with CM, sourced from the Hospital of the LSMU Kauno klinikos database, and 182 controls randomly selected from the Lithuanian Population Register in Kaunas City. Subject selection is published in our previous study (Semeklis et al.,2024). All participants underwent dermatological examination and completed surveys on personal/family history of skin cancer and sun exposure habits over the five years preceding the diagnosis of CM. We assessed skin type based on the Fitzpatrick scale as well as eye/hair color. Melanocytic nevi (MN) and freckles were counted using a standardized protocol from our previous studies (Kontautiene et al.,2015; Valiukeviciene et al., 2005). MN were categorized into groups based on sun exposure: maximal (face, neck,hands, ears, and shoulders), intermittent (chest, subscapular/lumbar regions, abdomen, outer upper arms, thighs,calves, and feet), and minimal (scalp, buttocks, armpits,inner forearms, palms, and soles). Variables between the CM subjects and the control group were compared using the chi-squared test, Student’s t-test, or the Mann-Whitney U-test. Binary logistic regression model with backward elimination was used to determine statistically significant risk factors for the prognosis of CM. Model fit data: the goodness-of-fit test (χ2 = 197.348, p<0.001), Nagelkerke’s R 2 = 0.618, and the Hosmer-Lemeshow test (χ2 = 11.577, p= 0.171) correctly classified 78.3% of CM cases and 87.5% of controls. Results: Mean age (M = 59.5, SD = 12.51 vs. M = 57.5,SD = 7.94) and sex (females: 62.1% vs. 62.8%) did not differ significantly (p = 0.075 and p = 0.892) between the CM subjects and the control group. The model revealed 5 risk factors that significantly increased the odds ratio of CM (OR; 95% confidence interval): tanning bed use vs.non use (6.46; 1.89–22.96), lack of sunscreen use vs. regular use (7.41; 2.88–19.09), and fair skin vs. medium/olive skin (2.06; 1.03–4.09). The probability of CM also increased with each instance of sunburn (2.57; 1.96–3.38) and with each additional MN >2 mm in sun-exposed areas (1.05;1.03–1.07). Conclusions: This is the first case-control study conducted in the Baltic Countries that identified CM risk factors in Lithuania, including tanning bed use, lack of sunscreen, high sunburn frequency, and melanocytic nevi in sun-exposed areas, highlighting the need for targeted prevention strategies.