Cancer risk in a population-based cohort of patients hospitalized for psoriasis in Sweden

Studies of clinical series of psoriasis patients have suggested an increased risk of nonmelanoma skin cancer and melanoma; the risk of other neoplasms has rarely been studied. In order to assess the incidence of cancer in a nationwide series of psoriasis patients from Sweden, we followed up, for the years 1965-89, 9773 patients with a hospital discharge diagnosis of psoriasis made during 1965-83, who were alive and free from malignancy 1 y after first discharge. We compared their incidence of neoplasms with that of the national population by computing standardized incidence ratios (SIR). We observed a total of 789 neoplasms [SIR 1.37, 95% confidence interval (CI) 1.28, 1.47]. There was an increase in the risk of cancers of the oral cavity and pharynx (SIR 2.80, 95% CI 1.96, 3.87), liver (SIR 1.91, 95% CI 1.28, 2.74), pancreas (SIR 1.56, 95% CI 1.02, 2.23), lung (SIR 2.13, 95% CI 1.71, 2.61), skin (squamous cell carcinoma, SIR 2.46, 95% CI 1.82, 3.27), female breast (SIR 1.27, 95% CI 1.00, 1.58), vulva (SIR 3.24, 95% CI 1.18, 7.06), penis (SIR 4.66, 95% CI 1.50, 10.9), bladder (SIR 1.43, 95% CI 1.03, 1.92), and kidney (SIR 1.56, 95% CI 1.04, 2.25). The risk of malignant melanoma was decreased (SIR 0.32, 95% CI 0.10, 0.74). Despite some limitations (possible diagnostic misclassification, lack of data on treatment, relatively short follow-up), our study provides evidence against an increased risk of melanoma among patients hospitalized for psoriasis. In addition to nonmelanoma skin and genital cancers, patients hospitalized for psoriasis were at increased risk of several malignancies, in particular those associated with alcohol drinking and tobacco smoking.