IgG4‐related sclerosing cholangitis may be a risk factor for cancer

Background/purpose The relationship between autoimmune pancreatitis and malignancy has been reported. However, the potential risk for cancer in patients with immunoglobulin 4-related sclerosing cholangitis (IgG4-SC) is unclear. The present study aimed to evaluate the incidence of cancer in IgG4-SC patients. Methods We retrospectively collected clinical data for 121 patients diagnosed with IgG4-SC from 7 hospitals. We calculated the standardized incidence ratio (SIR) of cancer in IgG4-SC patients based on the national cancer rates. The SIR of the period after the diagnosis of IgG4-SC were calculated. Results The mean follow-up period was 6.4 years, with 121 IgG4-SC patients. During the follow-up period, 26 patients had cancer, and 29 cancers were diagnosed. The SIR of cancer after the diagnosis of IgG4-SC was 1.90 (95% confidence interval [CI] 1.67-2.21). The SIR of pancreatic and bile duct cancer was 10.30 and 8.88, respectively. The SIR of cancer in 5 years after diagnosis of IgG4-SC were 2.58, 1.01, and 2.44, respectively. Conclusions IgG4-SC patients have a high risk of cancer including pancreatic and bile duct cancer. The risk of cancer was high less 5 years after diagnosis of IgG4-SC. Therefore, IgG4-SC patients may require careful long-term follow-up.