Lymphoma risk in psoriasis: results of the PUVA follow-up study.

OBJECTIVE To assess the risk of lymphoma in patients with psoriasis. DESIGN Prospective cohort study that spans 30 years and a systematic review of the literature. SETTING Sixteen university medical centers. PATIENTS A total of 1380 patients with psoriasis who were initially treated with psoralen-UV-A (PUVA) from 1975 through 1976 and who underwent periodic interviews and physician examinations irrespective of their use of any treatment. MAIN OUTCOME MEASURE Incidence of lymphoma relative to that expected in the general US population (original primary end point of the study). RESULTS The incidence of lymphoma in patients who received PUVA and were not exposed to high levels of methotrexate was comparable to that expected in the general population (incidence rate ratio, 0.85; 95% confidence interval, 0.37-1.67) but was elevated among those exposed to high levels of methotrexate (> or =36 months) (incidence rate ratio, 4.39; 95% confidence interval, 1.59-12.06). CONCLUSION Unless exposed to high levels of methotrexate, the risk of lymphoma among members of the PUVA Follow-up Study was comparable to that observed in the general population.