Background: There is strong epidemiologic evidence that psoriasis treatments may cause nonmelanoma skin cancer and possibly other types of cancer.
Objective: This study from Denmark reports the cancer incidence in 6910 patients with psoriasis discharged from the hospital from 1977 through 1987.
Methods: Patients were identified in the National Hospital Discharge Register and information on cases of cancer was obtained through the files of the Danish Cancer Registry; observed figures were compared with those expected on the basis of cancer incidence rates for the national population.
Results: A 2.5-fold increased risk was observed for nonmelanoma skin cancer in men and women, with no preponderance of any specific histologic subtype of cancer. In addition, excesses were seen of lung cancer in men (relative risk [RR] = 1.4) and women (RR = 1.6), of cancer of the larynx and pharynx in men (RR = 2.8 and 3.9), and of colon and kidney cancer in women (RR = 1.6 and 2.3).
Conclusion: The effect of cigarette smoking on the risk for noncutaneous cancer could not be assessed in this study; however, antipsoriatic treatment such as ionizing radiation and oral arsenicals must be considered as a possible cause of colon cancer, which has been observed in excess in two other studies of psoriatic patients.