By Will Boggs MD
NEW YORK (Reuters Health) - Treatment with tumor necrosis factor (TNF) inhibitors adds little to the already elevated risk of non-melanoma skin cancers in patients with rheumatoid arthritis (RA), according to a study from Sweden.
"With regards to squamous cell cancer and basal cell cancer, patients should feel safe to use TNF inhibitors (TNFi), but be observant for emerging skin lesions," Dr. Pauline Raaschou, from Karolinska Institutet, Stockholm, told Reuters Health by email. "Increased vigilance may be advisable in RA patients, whether the patient receives TNFi or not."
Previous studies have shown significantly higher rates of non-melanoma skin cancer in RA patients than in the general population, but studies of RA patients with TNFi have yielded mixed results.
Dr. Raaschou's team used data from the Swedish Biologics Register and the Swedish National Cancer Register to compare the relative risk of squamous cell skin cancer and basal cell cancer with RA and TNFi treatment.
RA patients not treated with TNFi were 88% more likely than the general population to have a first squamous cell cancer and 22% more likely than the general population to have a first basal cell cancer, according to the January 28 BMJ online report.
TNFi treatment further increased the risk of squamous cell cancer by 30%, which translated into a number needed to harm of more than 1,600.
The relative risks did not appear to increase with longer time on treatment or in patients with a history of a squamous cell cancer.
In contrast, the use of TNFi did not further increase the risk of basal cell cancer.
"Our findings imply that, whatever the mechanism, most of the increase in risk for squamous cell and basal cell cancer in rheumatoid arthritis patients treated with TNF inhibitors comes from factors other than that treatment," the researchers noted.
"Given the small absolute risk increase of skin cancer associated with TNFi in this study and the often excellent effect of these drugs, our results do not significantly shift the risk-benefit evaluation of TNFi in RA," Dr. Raaschou concluded.
"The main methodological limitation was that the authors were unable to adjust for severity of disease," wrote Dr. Shervin Assassi, from University of Texas Health Science Center at Houston, Houston, in a related editorial. "People with more severe arthritis would be more likely to receive TNF inhibitors. If severity of arthritis is related to risk of non-melanoma skin cancer, then this outcome is confounded by indication. Patients were not randomly assigned to treatments in this observational study, so any excess risk could be due to increased severity of disease rather than its treatment."
"This study provides further strong evidence that people with rheumatoid arthritis have an increased risk of non-melanoma skin cancer," he concluded. "Treatment with TNF inhibitors is associated with a modest extra risk of squamous cell cancer, but most of the overall risk originates from other factors including the disease itself. Therefore, all patients with rheumatoid arthritis -- regardless of treatment -- might benefit from increased surveillance for skin cancer and should be advised to protect themselves from the sun."
Several organizations funded this research. One coauthor reported receiving research funding from Pfizer and AstraZeneca.
SOURCE: https://bit.ly/1KsP1cB and https://bit.ly/1UOrZgQ
BMJ 2016.
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