Increased prevalence of malignancies in patients with IgG4-related disease: implications for clinical care.

Objectives: The association between cancer and IgG4-related disease (IgG4-RD) is evolving. The primary aim of this study was to investigate the prevalence of malignancies in IgG4-RD. The secondary aim was to describe the epidemiological and clinical characteristics of IgG4-RD patients with a history of cancer.

Methods: Two hundred and ten patients with IgG4-RD were included in this retrospective study. IgG4-RD phenotypes, clinical and serological variables were analysed. The prevalence of cancer in IgG4-RD was compared with that in the Italian population using the registry of the Global Cancer Observatory (GCO) of the World Health Organization. The Standardized Incidence Ratio (SIR) for cancer in IgG4-RD was obtained based on the 5-year Limited Duration Prevalence (2015-2020) of tumours in the Italian population.

Results: Thirty-seven/210 patients (18%) developed cancer before or after the diagnosis of IgG4-RD. Solid and haematologic tumours were more frequently observed in pancreato-biliary IgG4-RD. The SIR for malignancy in IgG4-RD patients was 2.54 higher than the general Italian population (P = 0.007). The SIR was 2.78 higher for males (P = 0.005) and 1.15 higher for females (P > 0.05). Thirty-two malignancies were diagnosed before and 16 after IgG4-RD diagnosis. Interval 'from IgG4-RD to cancer' was shorter than that 'from cancer to IgG4-RD'. Most tumours occurring after IgG4-RD developed within 36 months from diagnosis of IgG4-RD.

Conclusions: The prevalence of cancer in patients with IgG4-RD is increased compared with the Italian population and mechanistically suggests a possible paraneoplastic association. Close surveillance is warranted for the first 36 months after IgG4-RD diagnosis.