RISK OF HAEMATOLOGICAL MALIGNANCY IN PATIENTS WITH PSORIATIC ARTHRITIS, OVERALL AND IN RELATION TO TNF INHIBITORS - A NORDIC COHORT STUDY

• Several autoimmune inflammatory diseases, including rheumatoid arthritis (RA), are associated with increased risk of malignant lymphomas. There is also a longstanding concern of lymphoma development with tumour necrosis factor inhibitor (TNFi) treatment, but most studies in RA to date do not indicate an additionally increased risk. Corresponding studies in psoriatic arthritis (PsA), both with respect to the underlying risks, and risks in relation to treatment with TNFi, are limited. Data on myeloid malignancies in PsA are scarce.ObjectivesTo estimate the risk of haematological malignancy overall and by lymphoid and myeloid types in TNFi treated versus (vs.) biologics-naïve patients with PsA across the five Nordic countries. Additionally, we investigated the underlying risk of haematological malignancies in PsA as compared to the general population.MethodsWe identified patients with PsA starting a first ever TNFi from the clinical rheumatology registers (CRR) in Sweden (SE), Denmark (DK), Norway (NO), Finland (FI), and Iceland (ICE) from 2006 through 2019 (n=10 621). We identified biologics-naïve patients with PsA from a) the CRR (n=18 705, all countries) and b) the national patient registers (NPR, n=27 286, SE and DK only). To estimate the underlying risk of haematological malignancy in PsA, we randomly sampled general population comparators in SE and DK matched on year of birth, sex, and calendar year at start of follow-up, to the patients with PsA.Through linkage to the mandatory national cancer registers in all five countries, we collected information on haematological malignancy overall, and categorised into lymphoid or myeloid types. By applying a modified Poisson regression, we estimated pooled incidence rate ratio (IRR) with 95% confidence intervals (CI) for TNFi treated vs. biologics-naïve PsA and for PsA vs. the general population, adjusted for age (18-55, 56-65, 66-70, >70 years), sex, calendar period (2006-2010, 2011-2019) and country, and using robust standard errors.ResultsWe observed 40 events of haematological malignancies (during 59 827 person-years) among TNFi treated PsA, resulting in a crude incidence rate (IR) of 67 per 100 000 person-years. The corresponding IR was 91 (63 events) for biologics-naïve PsA from the CRR, and 118 (172 events) for biologics-naïve PsA from NPR. This resulted in a pooled IRR of 0.97 (0.69 to 1.37) for TNFi-treated vs. biologics-naïve PsA patients from the CRR, and 0.84 (0.64 to 1.10) vs. biologics-naïve PsA patients from the NPR. The pooled IRR of haematological malignancies in PsA overall vs. the general population was 1.35 (1.17 to 1.55). Throughout, the estimates were largely similar for lymphoid and myeloid malignancies (Figure 1). The crude IR of haematological malignancies were substantially akin across different TNFi agents.Figure 1.Pooled incidence rate ratios (IRRs) (95% CI) of haematological malignancy overall and by lymphoid and myeloid types, in first ever TNFi treated versus biologics-naïve patients with PsA, and versus general population comparators. Legend: Lymphoid malignancies include international classification of diseases (ICD) 10 codes C81-86, C88, C90-91. Myeloid malignancies include ICD10 codes C92-95, D45-D46, D47.1, D47.3-5. Incidence rate ratios adjusted for age (18-55, 56-65, 66-70, >70 years), sex, calendar period (2006-2010, 2011-2019) and country, and using robust standard errors.ConclusionIn this large five-country cohort study, we did not observe any increased risk of haematological malignancies overall, nor for lymphoid and myeloid types, in patients with PsA treated with TNFi. By contrast, there were signals of a moderately increased underlying risk of haematological malignancies, both of lymphoid and myeloid types, in patients with PsA overall as compared to the general population. The findings are of importance from a patient information perspective.AcknowledgementsWe would like to acknowledge the NordForsk and FOREUM, and especially the patient representatives of the NordForsk collaboration for their valuable contribution to this study.Disclosure of InterestsRené Cordtz: None declared, Johan Askling Consultant of: Abbvie, Astra-Zeneca, BMS, Eli Lilly, MSD, Pfizer, Roche, Samsung Bioepis, Sanofi, and UCB, Grant/research support from: Abbvie, Astra-Zeneca, BMS, Eli Lilly, MSD, Pfizer, Roche, Samsung Bioepis, Sanofi, and UCB, Bénédicte Delcoigne: None declared, Karin Ekström Smedby: None declared, Eva Baecklund: None declared, Christine Ballegaard: None declared, Pia Isomäki Speakers bureau: AbbVie, Eli Lilly and Pfizer, Consultant of: AbbVie, Eli Lilly, Pfizer, Roche and ViforPharma, Grant/research support from: Pfizer, Kalle Aaltonen: None declared, Björn Gudbjornsson Speakers bureau: Novartis, not related to this work, Consultant of: Novartis, not related to this work, Thorvardur Love Speakers bureau: Celgene, Sella Aa. Provan: None declared, Brigitte Michelsen Grant/research support from: Novartis, not related to this work, Joe Sexton: None declared, Lene Dreyer Speakers bureau: Eli Lilly, Galderma and Janssen, Grant/research support from: BMS not related to this work, Karin Hellgren: None declared

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