Patients with psoriasis may be at a greater risk of melanoma and hematologic cancers, compared with the general population, but treatments do not appear to increase risk, according to Shivani P. Reddy of the University of Illinois at Chicago, and associates.

In a retrospective cohort study, they identified 815,765 patients at Kaiser Permanente Southern California who had at least one medical encounter from January 2004 through December 2013. Of these patients, 8,161 (1%) met the diagnostic and inclusion criteria for psoriasis, and there were 7,167 (0.89%) cases of melanoma and 5,399 (0.66%) cases of lymphoma or leukemia.

Among the patients with psoriasis, there were 62 (0.87%) melanoma cases and 47 (0.87%) cases of lymphoma or leukemia.

Of the 109 patients with psoriasis who went on to develop melanoma or lymphoma, the time to diagnosis of melanoma or hematologic cancers was significantly less for patients with psoriasis than for patients without psoriasis (P = .01). The patients with psoriasis had a 1.53 times higher risk of developing a malignancy compared with patients without psoriasis (P less than .01) in the multivariable Cox proportional hazards model.