OBJECTIVES: Anemia is a frequent complication in cancer patients but few studies have evaluated the incidence of cancer among patients with iron deficiency anemia (IDA). We therefore investigated the association between IDA and incident colorectal and stomach cancer in Germany.

METHODS: This retrospective cohort study was based on data from the Disease Analyzer database (IQVIA). We included patients aged ≥18 years with IDA diagnosis between 2005 and 2021 in 1,284 general practices in Germany. Individuals without IDA diagnosis were matched to IDA patients using propensity score matching (1:1) based on age, sex, index year, average yearly consultation frequency during follow-up, and relevant co-diagnoses. All patients were free of colorectal and/or stomach cancer at inclusion to the cohort. We studied the association between IDA and incident colorectal and stomach cancer diagnosis using univariable Cox regression analysis.

RESULTS: 122,502 individuals with IDA and 122,502 individuals without IDA (mean age 54.2 years, 74.1% women) were included. After a maximum of 10 years of follow-up, 1.4% of IDA patients versus 0.8% of matched non-IDA patients were diagnosed with colorectal cancer, 0.3% of IDA patients versus 0.2% of matched non-IDA patients with stomach cancer. In the regression analysis, there was a considerable association between IDA and subsequent colorectal cancer (HR: 2.05; 95% CI: 1.83-2.30) as well as stomach cancer (HR: 1.41; 95% CI: 1.13-1.75). Subgroup analyses showed that patients >80 years and men had the strongest associations.

CONCLUSIONS: In this large retrospective cohort study in Germany, IDA was associated with subsequent colorectal and stomach cancer diagnoses, especially among patients >80 years and men.