Risk of malignancies in autoimmune hepatitis type 1 patients with a long‐term follow‐up in Japan

Aim The risk of malignancies in autoimmune diseases is high and is regarded to be due to immunological abnormalities, the use of immunosuppressive agents, and/or chronic inflammation. The aim of this study was to investigate the incidence and risk of malignancies in patients with autoimmune hepatitis (AIH) type 1 in Japan. Methods Two hundred and fifty‐six patients diagnosed with AIH were enrolled. A person‐year calculation was carried out for AIH patients, and the numbers of expected events were clarified using data from “The Monitoring of Cancer Incidence in Japan Project” in order to examine the standard incident rate (SIR) of each type of malignancy. Biochemical data regarding carcinogenesis and its background factors were also examined. Results Twenty‐seven patients (10.5%) developed malignancies; 11 (4.3%) with hepatobiliary cancer and 16 (6.3%) with extrahepatic malignancies. The overall SIR for malignancies in AIH was significantly high at 2.04 (95% confidence interval [CI], 1.34–2.96), and was high among female patients at 2.49 (95% CI, 1.60–3.71). The SIR for hepatobiliary cancer was 14.14 (95% CI, 7.05–25.30), and was markedly high for female patients at 21.83 (95% CI, 10.45–40.16). The SIR for oral/pharyngeal cancer was significantly high for female patients at 14.61 (95% CI, 1.64–52.77). The risk factors for hepatobiliary cancer at the diagnosis of AIH were low levels of alanine aminotransferase (P = 0.0226), low platelet counts (P