Risk of malignancy in patients with psoriasis: a 15-year nationwide population-based prospective cohort study in Korea

Background: The association between psoriasis and risk of malignancy has not been thoroughly evaluated in a large longitudinal cohort of Asian population. Objective: To determine the long-term risk of malignancy in Korean adult patients with psoriasis. Methods: We conducted a nationwide population-based prospective cohort study with a 15-year observational period. During the baseline period (1997–2000), total 1 773 786 Korean subjects who received health insurance from the National Health Insurance System were enrolled and 5788 subjects were defined as a psoriasis group. The number of new-onset malignancy was collected during the observational period (2001–2015). Results: Patients with psoriasis had a higher adjusted hazard ratio (aHR) for development of overall malignancy [aHR 1.08, 95% confidence interval (CI) 1.00–1.18] and gastric cancer (aHR 1.31, 95% CI 1.08–1.58) compared to controls. The risks of non-Hodgkin lymphoma and non-melanoma skin cancer were significantly increased only in patients with psoriasis who received systemic treatments (aHR 2.86, 95% CI 1.07–7.61 and aHR 3.93, 95% CI 1.47–10.47, respectively). Conclusion: Psoriasis is associated with long-term risk for overall malignancy in Koreans, which was primarily driven by the increased risk of gastric cancer.