Low risk of melanoma in patients with atopic dermatitis

Abstract

There is a possible association between atopy and cancer based on the concept of atopic diseases as a hyper-reactive state of the immune system. Melanoma is an immunogenic tumour, and since patients with atopic dermatitis (AD) are subjected to local and systemic immunosuppressives, it would be expected to find an influence of AD on the melanoma risk. There is a positive correlation between the number of naevi and melanoma risk, and children and adults with AD have fewer naevi than controls although many patients receive ultraviolet treatment. This study aims to investigate the melanoma risk in a retrospective cohort of AD patients compared with the population. 6280 AD patients born 1935-1979 visited five Dermatology clinics during 1986-2004. Mean follow-up time was 36.7 years (SD 6.9) corresponding to 230 742 person-years at risk. The cohort file was linked to the National Cancer register. Six AD patients with melanoma were identified, and the Poisson regression analysis adjusted for age group, sex and year resulted in an incidence rate ratio of 0.49 (95% confidence interval: 0.27-1.35, P = 0.08) for the AD group compared with the total population in the region. A low risk to develop melanoma was found in AD patients. However, the results must be interpreted with caution since the small number of expected cases of melanoma makes the risk estimate sensitive to chance effects. We hypothesize that formation of naevi and progression to melanoma is counteracted by the inflammatory process in the skin of AD patients.