Atopy May Protect Against Skin Cancer



LISBON – In the latest installment in an ongoing debate, dermatologist Thomas Kornek reported that atopic dermatitis was found to provide protection against skin cancer in patients in a large German study.

Standardized, onsite, dermatologist-conducted skin screenings of 90,880 employees in more than 300 German businesses demonstrated that the prevalence of nonmelanoma skin cancer among the 1.3% of workers with atopic dermatitis was less than half of that in coworkers without atopic dermatitis, Dr. Kornek reported at the congress.

Moreover, even though the subgroup with atopic dermatitis had significantly higher rates of well-established risk factors for melanoma, their actual prevalence of the malignancy was identical to that in workers without atopic dermatitis, implying a protective effect against melanoma as well, added Dr. Kornek of the University Medical Center Hamburg, Germany.

Participants in the workplace skin screening program averaged 43 years of age, and 53% were men. The prevalence of clinically diagnosed nonmelanoma skin cancer among patients with atopic dermatitis was 0.4%, compared with 0.9% in participants without atopy (P less than .05).

Premalignant skin lesions were identified in 1.7% of workers with atopic dermatitis and 2.1% of controls, a nonsignificant difference.

Melanomas were detected in 0.2% of participants with or without atopic dermatitis. Yet the prevalences of Fitzpatrick skin type I, more than 40 nevi, and a history of severe sunburns in childhood – all of which are risk factors for melanoma – were significantly greater in the atopic dermatitis subgroup, which in theory should have translated into more melanomas, said Dr. Kornek.

Two warring schools of thought have clashed with regard to the relationship between atopic dermatitis and cancer. One holds that the hyperreactive immune system that defines atopy in the form of asthma, hay fever, or atopic dermatitis ought to protect against carcinoma. The other school holds that the chronic immune stimulation present in individuals with atopic dermatitis ought to result in elevated risk. An additional consideration in patients with atopic dermatitis is that local and systemic immunotherapy could potentially boost the risk of developing skin cancer, noted Dr. Kornek.

Each side can point to supporting epidemiologic studies. For example, researchers in Sweden found that the risk of developing melanoma in 6,280 atopic dermatitis patients followed for more than 230,000 person-years was half that in the general Swedish population (J. Eur. Acad. Dermatol. Venereol. 2008;22:1423-8).

Dermatologists in Stockholm used the Swedish Cancer Registry to determine that a large cohort of atopic patients had no increased risk of nonmelanoma skin cancer, lymphoma, or cancer of the lung, pancreas, or cervix (Allergy 2005;60:1116-20).

Another group of investigators in Sweden reported modest but significantly increased risks of cancer of the pancreas, esophagus, lung, and brain, as well as lymphoma, in 15,666 patients earlier hospitalized for atopic dermatitis. There was a nonsignificant trend for more nonmelanoma skin cancers in the group, but no increase in melanoma (Arch. Dermatol. 2005;141:1123-7).

A literature review by dermatologists in Germany found mixed results regarding a possible association between atopy and cancer, although the investigators summed up the findings by noting that "the emerging picture from most of the currently available epidemiological data indicates that atopic disease is associated with a reduced risk of cancer" (Allergy 2005;60:1098-11).

Dr. Kornek speculated that one possible explanation for the reduced risk of skin cancer noted in the German workplace study is because individuals with atopic dermatitis are more aware of their skin and more alert to the rise of abnormal lesions than nonatopic persons.

He declared having no financial conflicts of interest.

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