The risk of cancer in patients with psoriasis: A population-based cohort study in Taiwan

Background An association between psoriasis and malignancy has been explored. However, no studies have been reported regarding cancer risk in Asian psoriasis populations. Objectives The aim of this study was to investigate the risk of cancer development in association with psoriasis. The effects of age at diagnosis, treatment modalities, and observation time were also evaluated. Methods Data for this retrospective population-based cohort study were obtained from the Taiwan National Health Insurance Research Database (NHIRD). This study included 3,686 patients with first-time diagnosis of psoriasis between 1996 and 2000. Another 200,000 patients without psoriasis served as the comparison group. All enrolled subjects were followed-up until the end of 2007. Cumulative incidences and hazard ratios (HRs) of cancer development were determined. Results Among the 3,686 psoriasis patients, 116 had incident cancers. The 7-year cumulative incidence of cancer among psoriasis patients was 4.8%. The adjusted HR for developing a cancer in association with psoriasis was 1.66 (95% confidence interval [CI], 1.38-2.00). Cancer risk was higher in male patients than in female patients (adjusted HR 1.86 vs.1.14, respectively). Certain cancers were significantly associated with psoriasis, including those of the urinary bladder and skin, followed by oropharynx/larynx, liver/gallbladder, and colon/rectum. Patients with psoriasis had an increased adjusted HR for cancer that varied by age. Younger patients with psoriasis tended to have the greatest risk of cancer. Finally, systemic phototherapy and oral medication did not significantly increase the risk of cancer. Phototherapy with UVB appeared to reduce the risk of cancer in psoriasis (adjusted HR, 0.52; 95% CI, 0.29-0.95; P = .03). Limitations NHIRD did not contain information regarding severity of psoriasis, status of smoking, alcohol use, family history of cancer, or diet. Misclassification of disease cannot be ruled out in a registry-based database. Conclusions Psoriasis carries an elevated risk of malignancies, especially in younger and in male patients. This effect is independent of systemic treatment for psoriasis. Finally, phototherapy with UVB did not increase, but rather reduced, the risk of cancer in psoriasis.