402. IgG4-RD and malignancy: Causal relationship or co-occurrence?

Background/ Objectives: IgG4-related disease (IgG4-RD) is a systemic immune-mediated disease with tumefactive lesions [1]. IgG4-RD sometimes presents with malignancy-like symptoms and may be mistaken for cancer or can be seen together with cancer. However, the data is scarce. In this study, we aimed to evaluate malignancies in a single-centre cohort of IgG4-RD. Methods: IgG4-RD patients who were referred to our vasculitis centre between Jan 2014 and Jun 2021 and fulfilled the Comprehensive Diagnostic Criteria for IgG4-RD were included in this study [2]. HUVAC database and hospital records were retrospectively evaluated for IgG4-RD patients’ age, gender, organ involvements, treatment details and malignancy history. Results: 97 IgG4-RD patients were assessed for malignancy. Six patients had been diagnosed as having malignancy, and the overall malignancy rate was %6.2. The figure shows the types of cancer and the temporal relationship between cancer and IgG4-RD diagnosis. Three patients have been diagnosed with IgG4-RD and malignancy simultaneously, and in the remainder, the diagnosis of cancer preceded the IgG4-RD by 1, 2, 9 and 23 years. No cases of malignancy were observed after the IgG4-RD diagnosis. Among IgG4-RD patients with a history of cancer four patients (66%) were smokers of former smokers. Conclusions: IgG4-RD could be related to different types of malignancies. But, the exact mechanism or causal relationship is still unknown. Development of synchronous cancer and IgG4RD at the same anatomic region might be associated with local auto-immunity, chronic local inflammation and cell-cycle dysregulation. Four of our patients having cancer history before IgG4RD diagnosis can be co-incidence or support the idea of IgG4-RD can arise in patients with a history of malignancy. A better understanding of the pathophysiologic relationship between cancer and IgG4-RD will provide better management of these patients. Disclosures: Professor Karadag: Received funding supprot Abbvie, Novartis, Roche, Viela-Bio, R-Pharm outside this study. Received consultancy fees and/or speaker fees from Abbvie, Abdi İbrahim, Amgen, Celltrion, Gilead, Farmanova, Lilly, Pfizer, Roche, UCB