Effects of aspirin at diagnosis on the survival of colorectal cancer patients: a 20-year population-based study

Previous studies have produced conflicting results regarding whether aspirin affects survival in colorectal cancer (CRC) patients. This study examines the relationship between regular aspirin use and survival in CRC patients within a nationwide cohort. All patients diagnosed with CRC in Iceland from 2000 to 2019 were identified through the Icelandic Cancer Registry. Clinical variables, including medications, were extracted from medical records. Overall survival (OS) and cancer-specific survival (CSS) were calculated. The follow-up period ended on 1 October 2022. The Charlson comorbidity index was used to assess comorbidity burden, and propensity score matching was employed to balance patient characteristics. Of the 2,561 eligible patients, 22% (<i>n</i> = 559) had been taking aspirin before their CRC diagnosis. Aspirin users were generally older and more frequently male (63% vs. 51%), with a higher comorbidity burden (15% vs. 4.7%). The median follow-up period was 51 months (IQR 14-110). Aspirin users were less likely to receive a stage IV diagnosis. After matching, overall survival (OS) was comparable between aspirin and non-users (HR: 0.94, 95% CI (0.83–1.06), <i>p</i> = 0.30). However, cancer-specific survival (CSS) was significantly better for aspirin users (HR: 0.79, 95% CI (0.65–0.95), <i>p</i> = 0.01). This benefit was not observed in patients with stages I–III CRC or those diagnosed due to gastrointestinal bleeding. Aspirin use was linked to improved CSS but not OS. The findings suggest aspirin’s potential role in slowing or hindering progression to stage IV cancer.