Autoimmune disease and subsequent digestive tract cancer by histology.

BACKGROUND Dysregulation of the immune function in autoimmune diseases could potentially lead to cancer development and there is definite evidence linking some autoimmune mechanisms with cancer. We analyzed systematically the occurrence of histology-specific digestive tract cancers in patients diagnosed with 33 different autoimmune diseases in order to address the question of shared susceptibility. PATIENTS AND METHODS Standardized incidence ratios (SIRs) were calculated for subsequent digestive tract cancers up to the year 2008 and in patients hospitalized for autoimmune disease after the year 1964. RESULTS Myasthenia gravis associated with five different cancers with SIRs ranging from 1.35 to 2.78. Pernicious anemia, Crohn disease, ulcerative colitis, systemic lupus erythematosis and psoriasis were also associated with cancers at multiple sites. Rheumatoid arthritis associated with no cancer and the standardized incidence ratio was decreased for colon adenocarcinoma, also in ankylosing spondylitis patients. CONCLUSIONS Increased risks of cancer were observed in patients with several autoimmune diseases. Myasthenia gravis and pernicious anemia were associated with many cancers; this is possibly related to immunosuppressant medication in myasthenia gravis. The decreased risks in colon and rectal adenocarcinomas in rheumatoid arthritis and ankylosing spondylitis suggest underlying inflammatory mechanisms as the risks may have been suppressed by the use of anti-inflammatory medication.