The risk of malignancy associated with psoriasis.

OBJECTIVE To measure the incidence of cancer in patients with psoriasis, stratified by the severity of their disease. DESIGN A cohort study. SETTING Administrative claims records obtained from Medicaid programs in 3 US states. PARTICIPANTS All individuals in the claims database who qualified for 1 of the 5 following groups: severe psoriasis as defined by treatment with systemic medication, less severe psoriasis, severe eczema, history of organ transplantation, and hypertension. MAIN OUTCOME MEASURE A diagnosis of cancer. RESULTS Individuals with severe psoriasis were more likely to develop a malignancy than those with hypertension (risk ratio, 1.78; 95% confidence interval [CI], 1.32-2.40). The risk of malignancy in the severe psoriasis group approaches that in patients with organ transplants (risk ratio, 2.12; 95% CI, 1.80-2.50). Most of these cancers were nonmelanoma skin cancers and lymphoproliferative malignancies. Those with less severe psoriasis were only slightly more likely to develop a new malignancy than those with hypertension (risk ratio, 1.13; 95% CI, 1.03-1.25). CONCLUSIONS Patients with psoriasis are at an increased risk of developing a malignancy compared with patients with hypertension. The increased risk is greatest for those with severe disease (ie, patients with psoriasis treated with systemic agents) and minimal (if an increased risk at all) for those with less severe disease compared with those in the hypertension group. The increased risk is mainly for lymphoproliferative cancers and nonmelanoma skin cancers.