Do steroids increase lymphoma risk?: A case-control study of lymphoma risk in polymyalgia rheumatica/giant cell arteritis

Background: Recent studies indicate increased risks of malignant lymphomas among individuals treated with corticosteroids, but have not taken into account the underlying reasons for steroid use, so the increased risks might be attributable to the underlying disease or concomitant treatments other than steroids. Polymyalgia rheumatica (PMR) and temporal arteritis (giant cell arteritis, GCA) are common inflammatory conditions treated with steroids as single immunosuppressive therapy, but data on lymphoma risk in GCA/PMR are limited. Objective: To assess the risk of lymphoma associated with steroid treatment of GCA/PMR. Methods: The association between GCA/PMR and malignant lymphomas (overall, and separately for non-Hodgkin lymphoma, Hodgkin lymphoma, and chronic lymphatic leukaemia) was examined in a nationwide, population based, case-control study of 42 676 lymphoma cases and 78 487 matched population controls, using prospectively recorded data on lymphomas from the Swedish cancer register 1964-2000 and data on pre-lymphoma hospital admissions for GCA/PMR from the Swedish inpatient register 1964-2000. Odds ratios (OR) associated with a pre-lymphoma hospital admission for GCA/PMR were calculated using conditional logistic regression. Results: 153 lymphoma cases and 345 population controls had a history of GCA/PMR, resulting in an overall OR for malignant lymphomas of 0.81 (95% confidence interval, 0.67 to 0.98). The OR varied little with lymphoma type, sex, age, and calendar period. The OR for GCA was 0.67 (0.48 to 0.98) and for PMR, 0.83 (0.67 to 1.04). Conclusions: Treated GCA is not associated with increased lymphoma risks, which suggests that even at considerable cumulative doses, steroids may not appreciably increase lymphoma risk.