Risk of Non-Hodgkin's Lymphoma in Primary Sjogren's Syndrome: A Population-Based Study

Objective Primary Sjogren's syndrome (SS) is associated with an increased risk of non-Hodgkin's lymphoma (NHL), but the reported prevalence and risk vary considerably. The objective of this study was to determine the risk of NHL in a well-defined population-based primary SS cohort in Norway. Methods The authors examined all patients fulfilling the AmericanEuropean Consensus Group criteria for primary SS from 2 Norwegian counties and compared the data to the Cancer Registry of Norway to identify the primary SS patients who had lymphoma. In addition, lymphoma patient files from the same period were reviewed for undiagnosed primary SS to ensure the quality of registry data. Results As of July 1, 2009, 443 living subjects with primary SS were identified in an area with 896,840 inhabitants, which is 18.6% of the total population of Norway. Seven cases of NHL (1.6%) were found during a total followup of 3,813 person-years, resulting in a standardized incidence ratio of 9.0 (95% confidence interval 7.126.3) for NHL in primary SS patients. Conclusion The risk of NHL in patients with primary SS in Norway is increased 9 times compared with the general population. This is in accordance with recent studies, and the quality and completeness of the registries and strict use of diagnostic criteria support the validity of the results.