Tanning bed exposure in association with multiple primary melanoma.

Abstract

e22107 Background: Patients with primary cutaneous melanoma are at increased risk of subsequent new primary melanoma. Indoor tanning is a risk factor for melanoma. The primary objective of this study was to determine the association between indoor tanning and multiple primary melanoma (MPM). The secondary objective was to compare clinical and pathological characteristics of primary and secondary malignant melanoma. Methods: This retrospective case-control study of MPM and gender-matched controls with single primary melanoma retrieved at 2:1 ratio from the University of Pittsburgh Cancer Institute Melanoma Center Biological Sample and Nevus Bank from January 1996 through October 2019. Logistic regression models were used to examine the association between MPM and risk factors. Results: In total, 330 patients (39.1% men; median [SD] age, 51 [15] years) were enrolled, including 110 with single and 220 with MPM. Median time between diagnosis of first and second primary melanoma was 13 months. 22.7% of patients with MPM had 3 or more primary melanomas. Compared with patients who had a single primary melanoma, patients with multiple melanomas were younger at diagnosis of first melanoma (median age 46 vs 52, p = 0.006), more likely to be discovered at Stage 0 and 1 (68% vs 49%, p < 0.0001), and to have had indoor tanning exposure (34% vs 10%, p < 0.0001), family history of melanoma (18% vs 8%, p = 0.0045), atypical moles (37% vs 13%, p < 0.0001), dysplastic nevi (21% vs 5%, p < 0.0001), and Breslow thickness of less than 1 mm (61% vs 33%, p < 0.0001). Compared with the patient’s first melanoma, subsequent melanomas were more likely to be thinner (0.6mm vs 1.2mm, p = 0.0007) or in situ (24% vs 13%, p = 0.0004). The estimated probability of locus that was the same for first and second primary melanomas was 34% with (95% CI 25%, 44%). The most common location for second primary melanoma was upper extremity (34%). In univariate analysis, lifetime tanning bed exposure of > 10 sessions was associated with an increased risk of second primary melanoma OR 4.60 [95% CI, 2.52-8.42, p < 0.0001]. In multivariate analysis after adjusting for age, family history of melanoma, presence of atypical and dysplastic nevi, recreational sun exposure, indoor tanning remained significantly associated with MPM (OR 4.32 [95% CI, 1.54-12.15, p = 0.0026]). Conclusions: Indoor tanning for > 10 sessions is associated with increased risk of second primary melanoma. Subsequent melanomas are more likely to be thin or in situ, and to occur in different anatomic locations.