Atrial Fibrillation, Anticoagulants, and CRC Outcomes: A Nationwide 20-Year Study.

Colorectal cancer (CRC) is a leading cause of cancer-related death and presents most often with occult or overt gastrointestinal bleeding (GIB). Oral anticoagulation (OAC) use has been hypothesized to increase the rate of GIB events and potentially cause early detection of CRC. This study aimed to investigate whether prior use of OAC could decrease overall or cancer-specific mortality in patients with CRC.All patients with CRC in Iceland from 2000 to 2019 were identified from the Icelandic Cancer Registry. Through a detailed review of medical records, clinical data were obtained. Comorbidity was assessed using the Charlson comorbidity index. Inverse probability weighting was used to balance the study groups.Of 2,563 patients, 173 were taking OACs due to atrial fibrillation and were diagnosed with CRC. OAC users were predominantly older males with a higher comorbidity index. While staging was not significantly different, tumor size and lymph node metastases were different. After weighting, OAC users had a similar overall mortality (HR = 1.08; 95% CI, 0.91-1.28,  = 0.37), but lower CRC-specific mortality (HR = 0.75; 95% CI, 0.57-1.00,  = 0.046), specifically in the first 5 years. Cardiovascular mortality was significantly higher in OAC users.Patients on OACs due to atrial fibrillation had lower CRC-specific mortality, suggesting that OAC use could be associated with survival benefits through early detection of CRC. However, these results should be interpreted carefully due to substantial competing cardiovascular mortality.