according to two matched longitudinal cohort studies from England and Denmark.
“In this study, no evidence was found that people with atopic eczema are at increased risk of most cancers. An exception is the observed association between atopic eczema and lymphoma, particularly NHL, [which] increased with eczema severity,” Kathryn E. Mansfield, PhD, wrote in JAMA Dermatology. Adjusted hazard ratios for NHL in the English cohort were 1.06 (99% CI, 0.90-1.25) for mild atopic eczema, 1.24 (99% CI, 1.04-1.48) for moderate eczema, and 2.08 (99% CI, 1.42-3.04) for severe eczema, reported Dr. Mansfield of the London School of Hygiene and Tropical Medicine and associates.
Past studies of a possible link between atopic eczema and cancer have produced conflicting evidence, which might reflect “two competing theories” – that cancer risk falls with greater immune surveillance, and that cancer risk rises with immune stimulation, the researchers wrote. Immunosuppressive treatment and an impaired skin barrier might also increase the risk of cancer, but the evidence is conflicting.
For the study, they analyzed electronic health records linked with hospital admissions and death records in England and national health registry data from Denmark. The English cohort included 471,970 adults with atopic eczema and 2,239,775 adults without atopic eczema. The Danish cohort was composed of individuals of any age, including 44,945 who had eczema and with 445,673 who did not. Participants were matched based on factors such as age, sex, and primary care practice. The researchers excluded individuals with a history of cancer, apart from nonmelanoma skin cancer or keratinocyte cancer. (For analyses of skin cancer risk, they also excluded individuals with a history of nonmelanoma skin cancer.)
Overall, there was “little evidence” for a link between atopic eczema and cancer (adjusted hazard ratio in England, 1.04; 99% CI, 1.02-1.06; aHR in Denmark, 1.05; 99% CI, 0.95-1.16) or for most specific types of cancer, the investigators wrote.
In England, however, eczema was associated with a significantly increased risk for noncutaneous lymphoma, with an adjusted HRs of 1.19 (99% CI, 1.07-1.34) for NHL, and 1.48 (99% CI, 1.07-2.04) for Hodgkin lymphoma. Lymphoma risk was highest among adults with severe eczema, defined as those who had been prescribed a systemic treatment for their disease, who had received phototherapy, or who had been referred to a specialist or admitted to a hospital for atopic eczema. Point estimates in the Danish cohort also revealed a higher risk for lymphoma among individuals with moderate to severe atopic eczema, compared with those with eczema, but the 99% CIs crossed 1.0.
Dr. Shadmehr Demehri
The findings highlight the need to be aware of, screen for, and study the pathogenesis of heightened lymphoma risk among patients with atopic eczema, said Shawn Demehri, MD, PhD, of the department of dermatology and cancer center, at Massachusetts General Hospital, Boston, who was not involved in the study.
“Prospectively collected data from large cohorts of eczema patients is a strength of this study,” he said in an interview. “However, the age range included in the study is suboptimal for assessing cancer as an outcome. The lower incidence of cancer in younger individuals hinders the ability to detect differences in cancer risk between the two groups.” (Approximately 57% of individuals in the English cohort were aged 18-44 years, while approximately 70% of those in the Danish cohort were less than 18 years.)
Understanding how eczema affects the risk of non-Hodgkin lymphoma is an important future direction of research, Dr. Demehri emphasized. “The landscape of atopic eczema therapeutics has dramatically changed in the recent years. It will be very interesting to determine how new biologics impact cancer risk in eczema patients.”
Partial support for the work was provided by the Wellcome Trust, the Royal Society, the Dagmar Marshalls Fund, and the Aase and Ejnar Danielsens Fund. Dr. Mansfield disclosed support from a Wellcome Trust grant. Her coinvestigators disclosed ties to TARGET-DERM, Pfizer, and GlaxoSmithKline, and from the Wellcome Trust, Medical Research Council, the National Institute for Health Research, the British Heart Foundation, Diabetes UK, and IMI Horizon 2020 funding BIOMAP. Dr. Demehri reported having no relevant conflicts of interest.
SOURCE: Mansfield KE et al. JAMA Dermatol. 2020 Jun 24. doi: 10.1001/jamadermatol.2020.1948.