Host characteristics and risk of incident melanoma by Breslow thickness

Background: Several host characteristics, including pigmentary traits (hair color, sunburn susceptibility and tanning ability), number of common nevi (moles), and family history of melanoma, have been associated with risk of melanoma. Methods: We prospectively examined the associations between host characteristics and risk of incident melanoma by Breslow thickness (1 mm, thin melanoma; or >1 mm, "thicker melanoma") based on the Nurses' Health Study (NHS, n = 86,380 women), NHS II (n = 104,100 women), and Health Professionals Follow-up Study (HPFS, n = 46,934 men). Results: During 22–30 years' follow-up, a total of 1,813 incident melanoma cases were identified with information on Breslow thickness, 1,392 (76.8%) of which had thin melanoma. No significant differences were observed for thin and thicker melanoma in associations with hair color, sunburn susceptibility, and tanning ability. However, we found significant differences for the association with family history of melanoma, with a higher risk estimate for thicker melanoma [HR = 2.55; 95% confidence interval (CI): 1.91–3.42] than thin melanoma (HR = 1.59; 95% CI: 1.21–2.08; P _{heterogeneity} = 0.02). Interestingly, women and men displayed differential associations between nevi count and risk of melanoma by Breslow thickness, with the association appearing stronger for thicker melanoma than thin melanoma in men (P _{heterogeneity} = 0.01), but not in women. Conclusions: Individuals with family history of melanoma may be more likely to develop thicker melanoma. Men with high number of common nevi may tend to develop thicker melanoma, which was not found for women. Impact: The findings further stress the risk of thicker melanoma for individuals with a family history of melanoma and men with a high nevi count.