Risk of melanoma following keratinocyte malignancies.

Patients diagnosed with keratinocyte cancer experience heightened risk for melanoma, yet patients who go on to develop this malignancy have not been well-characterized. We followed a population-based cohort of 2243 participants with histologically confirmed KC identified from dermatology and pathology practices who did not have a history of internal malignancy (1363 BCC, 880 SCC). A total of 77 participants went on to develop melanoma. Individual-level data were collected via personal interviews including demographic information and skin cancer risk factors, as well as KC tumor characteristics such as anatomic site and histologic subtype. Using adjusted Cox proportionate hazards models, older patients (age 61 or older vs 60 or younger) were at twofold increased risk for developing melanoma following KC (age 61-65 HR = 2.5; 95% CI = 1.3-4.6) (age > 65 HR = 2.0; 95% CI = 1.2-3.4) and women were at reduced risk compared to men (HR = 0.5; 95% CI = 0.3-0.8). Among patients with BCC, those with tumors on the trunk/limbs compared to the head/neck were at greater risk for subsequent melanoma (HR = 2.7; 95% CI = 1.3-5.7). Subsequent risk of melanoma also related to established risk factors including blond/red vs dark hair (HR = 1.9; 95% CI = 1.1-3.4), tendency to burn rather than tan (HR = 1.7; 95% CI = 1.0-2.7), ≥1 nevi on their back compared to no nevi (HR = 2.2; 95% CI = 1.2-3.8) and a history of ≥1 painful childhood sunburns vs none (HR = 2.1; 95% CI = 1.2-3.6). Thus, in addition to pigmentary traits, ultraviolet radiation (UVR)-related factors and clinical features of KC such as anatomic site may be useful in identifying patients at increased risk for melanoma after KC.