The five major autoimmune diseases increase the risk of cancer: epidemiological data from a large‐scale cohort study in China

BACKGROUND: Cancer incidence and mortality have received critical attention during the long‐term management of morbidities in patients with autoimmune diseases (AIDs). This study aimed to investigate and compare the risk of cancer associated with five major AIDs in a large‐scale Chinese cohort. METHODS: A total of 8,120 AID patients consecutively admitted to a national tertiary referral center in China were included and followed‐up for 38,726.55 patient‐years, including those with systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), Sjögren's syndrome (SS), systemic scleroderma (SSc), and idiopathic inflammatory myositis (IIM). Demographic data, cancer incidence, predilecting sites and cancer onset time were recorded and compared among the five AIDs. RESULTS: Four hundred and thirty (5.3%) patients developed cancer. Their median age was 57.5 years and AID duration was 79.8 months. The estimated total standardized incidence ratio (SIR) of cancer in AIDs patients was 3.37, with the highest SIR observed in IIM (4.31), followed by RA (3.99), SSc (3.77), SS (2.88) and SLE (2.58). The increased SIR of cancers in AID patients showed a female predominance (female vs. male: 3.59 vs. 2.77) and younger patient involvement (age <50 vs. ≥50 years: 4.88 vs. 3.04). Patients with SLE had increased SIRs for developing hematologic malignancies and solid tumors located in the urinary bladder, corpus uteri and cervix uteri. Patients with SS had a significantly high SIR for developing non‐Hodgkin's lymphoma. Within 3 years of IIM diagnosis, 74.6% of the patients developed cancer and they had a high risk of ovarian cancer. RA was associated with a wide distribution of scancers, including non‐Hodgkin's lymphoma, gynecologic, urinary tract, thyroid gland and lung cancers. SSc patients had increased SIRs for developing cervical uterine, lung, and breast cancers. CONCLUSION: Patients with five major AIDs in China had an increased risk of developing cancer, with a predominance in women and younger patients, although cancer incidence, predilection sites and cancer onset time may vary greatly in each AID entity.