Are people with atopic dermatitis at a higher or lower risk of developing skin cancer? Researchers found conflicting evidence.
Patients with atopic dermatitis (AD) often try to get more sun to treat their ailment. Does that exposure or other AD therapies increase their risk of developing skin cancer?
A recent study conducted by Sara Gandini, PhD, of the Division of Epidemiology and Biostatistics at the European Institute of Oncology in Milan, Italy, and colleagues, published in the Journal of Dermatological Science investigated whether AD patients have a greater risk of skin malignancy.
In describing their reasons for the study, the researchers state, “The initial observation of an inverse association between AD and body naevi count in pediatric populations gave rise to the hypothesis that the risk of melanoma may be reduced among AD patients.”
Although several studies addressed the question of a link between atopic dermatitis and skin cancer, the results were conflicting, leading the researchers to say, “To help clarify this issue, we conducted a review of the literature and meta-analysis of all published papers focusing on the association between atopic dermatitis, body naevi count, and the risk of cutaneous melanoma and keratinocyte skin cancer.” A total of 18 papers was included in the final analysis.
The reviewers found what they describe as “fairly convincing evidence” that AD patients have a lower naevi count than the general population. The available data about the relationship between AD and melanoma risk, the reviewers say “are rather more conflicting.” They go on to say, “Most likely, the main reason for this is the heterogeneity across published papers in terms of study design and study subjects,” adding that “multiple sources of bias make it difficult to draw firm conclusions on the association between atopic dermatitis and melanoma risk.”
In examining the research on AD and keratinocyte skin cancer (KSC), the researchers say “the evidence in favor of an association between atopic dermatitis and KSC risk became convincing” by excluding one study, which found a lower risk of KSC among AD patients. “Reasons for this discrepancy,” say the researchers, “may be the reliance on KSC self-reporting as a possible inclusion criterion for cases; the use of patients with benign dermatological conditions among controls; the assessment of AD symptoms via mail survey; and the lack of adjustment for phenotypic characteristics and exposure to sunlight.”
The reviewers note that phenotype and exposure to UVB radiation are both major risk factors for melanoma and KSC, yet exposure to sunlight can reduce the symptoms of AD. Thus, it is possible that AD patients expose themselves to sunlight more than others. Additionally, many of the studies on AD and skin cancer frequently “lack information about topical and/or systemic treatments administered prior to recruitment,” say the authors, adding that most of the systemic treatments used in AD “may have a potential carcinogenic effect.” One last limitation to such studies is surveillance bias: AD patients are more likely to have skin examinations, and so more likely to receive a diagnosis of skin cancer.
Those limitations, taken together, lead the authors to state, “the unsatisfactory internal validity and non-comparability of studies published so far prevent from giving a clear-cut answer to the question of whether subjects with AD are at increased or reduced risk of skin cancer compared to the general population.” However, better safe than sorry, they say, concluding, “Despite the lack of strong scientific evidence, we recommend that subjects receiving a diagnosis of atopic dermatitis are given advice by dermatologists and pediatricians to avoid an excessive exposure to sunlight, and instructed on the importance to check their skin regularly and consult a doctor in case of a suspicious lesion, whether pigmented or not.”
For further reading: New AD drugs needed. Atopic dermatitis increases risk of other diseases.