Background Hospitalized psoriasis patients are known to have a higher risk of malignancy (e.g., nonmelanoma skin cancer [NMSC], lymphoma, and melanoma) than the general population; currently, it is unclear whether this risk is affected by psoriasis severity. The aim of this study was to compare the cancer risk of patients with mild and severe psoriasis and the general population.
Methods Data for this retrospective population-based cohort study were obtained from the Taiwan National Health Insurance Research Database. This study included 7061 patients with a first-time diagnosis of psoriasis. All study individuals were followed up until the end of 2007. The crude incidence density ratio and standardized incidence ratio (SIR) of NMSC, melanoma, and lymphoma were determined.
Results Among psoriasis patients, the most common cancer was NMSC (density ratio: 7.5); women were at a higher risk of NMSC than men (density ratios: 8.08 vs. 7.0). Psoriasis patients in the south geographic group or in the 50- to 59-year-old age group were most likely to develop NMSC. The NMSC SIR was higher among patients with severe psoriasis than among patients with mild psoriasis (SIR: 3.72 vs. 7.08). The lymphoma and melanoma SIR among patients with severe psoriasis was also high (lymphoma SIR: 4.85; melanoma: 11.01).
Conclusions Psoriasis carries an elevated risk of NMSC and lymphoma. This effect is modified by the severity of psoriasis, age, gender, and geographic location.