Importance: The risk of cancer in patients with psoriasis remains a cause of special concern due to the chronic inflammatory nature of the disease, the use of immune-suppressive treatments and UV therapies, and the increased prevalence of comorbid, well-established risk factors for cancer, such as smoking and obesity, all of which may increase the risk of carcinogenesis.
Objective: To compare the overall risk of cancer, and specific cancers of interest, in patients with psoriasis compared with patients without psoriasis.
Design, setting, and participants: Population-based cohort study of patients ages 18 to 89 years with no medical history of human immunodeficiency virus, cancer, organ transplants, or hereditary disease (albinism and xeroderma pigmentosum), prior to the start date, conducted using The Health Improvement Network, a primary care medical records database in the United Kingdom. The data analyzed had been collected prospectively from 2002 through January 2014. The analysis was completed in August 2015.
Exposures of interest: Patients with at least 1 diagnostic code for psoriasis were classified as having moderate-to-severe disease if they had been prescribed psoralen, methotrexate, cyclosporine, acitretin, adalimumab, etanercept, infliximab, or ustekinumab or phototherapy for psoriasis. Patients were classified as having mild disease if they never received treatment with any of these agents.
Main outcomes and measures: Incident cancer diagnosis.
Results: A total of 937,716 control group patients without psoriasis, matched on date and practice visit, and 198,366 patients with psoriasis (186,076 with mild psoriasis and 12,290 with moderate-to-severe disease) were included in the analysis. The adjusted hazard ratios (aHRs) with 95% CIs for any incident cancer excluding nonmelanoma skin cancer (NMSC) were 1.06 (95% CI, 1.02-1.09), 1.06 (95% CI, 1.02-1.09), and 1.08 (95% CI, 0.96-1.22) in the overall, mild, and severe psoriasis group. The aHRs for incident lymphoma were 1.34 (95% CI, 1.18-1.51), 1.31 (95% CI, 1.15-1.49), and 1.89 (95% CI, 1.25-2.86); for NMSC, 1.12 (95% CI, 1.07-1.16), 1.09 (95% CI, 1.05-1.13), and 1.61 (95% CI, 1.42-1.84); and for lung cancer, 1.15 (95% CI, 1.03-1.27), 1.12 (95% CI, 1.01-1.25), and 1.62 (95% CI, 1.16-2.28) in the overall, mild, and severe psoriasis groups, respectively. No significant association was seen with cancer of the breast, colon, prostate, or leukemia.
Conclusions and relevance: The association between psoriasis and cancer, albeit small, was present in our cohort of patients with psoriasis. This association was primarily driven by NMSC, lymphoma, and lung cancer.