Prevalence, Incidence, and Risk of Cancer in Patients With Psoriasis and Psoriatic Arthritis

Importance: The association between psoriasis and risk of cancer remains debatable. Objective: To evaluate the association and risk of cancer in patients with psoriasis or psoriatic arthritis, including risk of specific cancer subtypes. Data Sources: Two databases (PubMed and Embase) were screened from inception to January 1, 2019, using the search string psoriasis or psoriatic and neoplasms or malignancy or cancer. The search was filtered to only include human participants and publications in English. Study Selection: Observational cohort studies with a population of patients with psoriasis or psoriatic arthritis were included. Studies had to be original and report the incidence or prevalence of cancer within this population. Studies evaluating pediatric populations and cancer types not included in the protocol were excluded. Data Extraction and Synthesis: This study was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. The search string, objectives, and study protocol methods were defined before the study was initiated. A total of 365 studies were included for full-text assessment. Owing to the heterogeneity of the included studies, a random-effects model was used. Main Outcomes and Measures: Main outcome was cancer (overall and specific subtypes) and measures were prevalence, incidence, and risk estimate for cancer in patients with psoriasis or psoriatic arthritis. Results: Of the 365 studies assessed, 112 were included in the analysis (N = 2 053 932 patients). The overall prevalence of cancer in patients with psoriasis was 4.78% (95% CI, 4.02%-5.59%), with an incidence rate of 11.75 per 1000 person-years (95% CI, 8.66-15.31) and a risk ratio (RR) of 1.21 (95% CI, 1.11-1.33). There was an increased risk of several cancers, including keratinocyte cancer (RR, 2.28; 95% CI, 1.73-3.01), lymphomas (RR, 1.56; 95% CI, 1.37-1.78), lung cancer (RR, 1.26; 95% CI, 1.13-1.40), and bladder cancer (RR, 1.12; 95% CI, 1.04-1.19). No increased risk of cancer for patients with psoriasis treated with biologic agents was found (RR, 0.97; 95% CI, 0.85-1.10). Psoriatic arthritis was not associated with increased risk of cancer overall (RR, 1.02; 95% CI, 0.97-1.08). Conclusions and Relevance: Patients with psoriasis appear to have a slightly increased risk of cancer, particularly keratinocyte cancer and lymphomas. Data on treatment with biologic agents did not show an increased risk of cancer. Data on cancer in patients with psoriatic arthritis remain scarce, and further research is warranted in this area.