A meta-analysis of more than 1.5 million patients found that several autoimmune diseases are linked to differing risks of developing digestive system cancers. The study analyzed 47 observational studies and identified both higher and lower risks depending on the disease and cancer type.

Researchers examined celiac disease, systemic lupus erythematosus (SLE), multiple sclerosis (MS), and type 1 diabetes (T1D) in relation to cancers of the pancreas, stomach, esophagus, small intestine, colon, rectum, liver, and gallbladder. Strict bias assessments were applied to improve the reliability of results.

Celiac disease was associated with higher risks of pancreatic, esophageal, colon, liver, and hepatobiliary cancers. The strongest link was with small intestine cancer, with more than a four-fold increased risk compared with the general population. No increased risk was seen for stomach, rectal, or overall colorectal cancers.

SLE was associated with higher risks of pancreatic, esophageal, colon, liver, and hepatobiliary cancers. A previous report associated with stomach cancer was not observed after adjusting for outlier data.

MS was associated with lower risks of pancreatic, esophageal, rectal, and colorectal cancers. No significant associations were found with other digestive system cancers.

T1D was linked to higher risks for most digestive system cancers except those of the small intestine and rectum. Elevated risks included stomach, esophageal, colon, liver, gallbladder, hepatobiliary, and pancreatic cancers.

The study followed systematic review and meta-analysis guidelines and included data from major medical databases through May 2025. The Risk Of Bias In Non-randomized Studies of Exposures tool was used to evaluate risk of bias. Random-effects models were applied to pool risk estimates, and sensitivity analyses addressed outliers and other potential biases.

Most included studies were observational and had a serious risk of bias from unmeasured confounding. The analysis could not assess how specific treatments may influence cancer risk. Data for some cancer types were limited, and most studies were in English or German, potentially excluding other relevant research. Variability in diagnostic criteria, follow-up periods, and population characteristics may also have affected results. Further research is needed to understand underlying mechanisms and evaluate the influence of treatments on cancer risk.

The authors reported no conflicts of interest.

Source: eClinical Medicine