Effect of autoimmune diseases on mortality and survival in subsequent digestive tract cancers.

BACKGROUND: Patients with some autoimmune diseases (AIDs) are at increased risk of cancer, possibly a result of an underlying dysregulation of the immune system, medication, treatment or, probably, surveillance bias. Data on cancer mortality and survival in patients previously diagnosed with AIDs would provide novel information on these comorbidities and their clinical implications. PATIENTS AND METHODS: Standardized mortality ratios (SMRs) and hazard ratios (HRs) were calculated for subsequent deaths from seven digestive tract cancers between 1964 and 2008 in patients hospitalized for any of 33 AIDs.
RESULTS: There were 33 increased SMRs for specific cancers after a defined AID; similarly, 21 HRs were increased. Both the SMR and HR were increased after 10 autoimmune disorders, including pernicious anemia, systemic lupus erythematosus and psoriasis. Increased SMRs and unchanged HRs were noted for 23 cancers. Myasthenia gravis was associated with SMRs for five cancers but no increases in HRs. For nine cancers, including esophageal cancer after ulcerative colitis and rheumatoid arthritis, the SMR was unchanged but the HR increased.
CONCLUSIONS: The increases in SMRs provide evidence that cancer risks were truly increased and largely unaffected by surveillance bias. The prognostic survival data should contribute to clinical evaluation and therapeutic planning.