Comparison of Acute Colorectal Cancer Presentations Before and After the Introduction of a Bowel Screening Programme: A Single‐Centre Retrospective Cohort Study

BACKGROUND: The Bowel Screening Programme (BSP) in Aotearoa, New Zealand, was introduced to facilitate earlier detection of colorectal cancer (CRC), yet its impact on acute CRC presentations remains incompletely characterised. This study evaluated changes in the incidence and clinical features of acutely presenting, previously undiagnosed CRC before and after BSP implementation. METHODS: A single-centre retrospective cohort study was conducted at North Shore Hospital, Auckland. Adults (≥ 16 years) acutely admitted with a first diagnosis of CRC were identified in the 3 years preceding the BSP pilot (2009-2011) and the 3 years following national rollout (2018-2020). The primary outcome was the age-standardised population incidence of acute CRC. Incidence rate ratios (IRRs) were estimated using age-adjusted Poisson regression. RESULTS: Three-hundred twenty three patients were included (pre-BSP n = 215; post-BSP n = 108). The age-standardised incidence of acute CRC declined from 9.71 per 100 000 population (95% CI: 7.56-12.27) in 2009 to 3.79 per 100 000 (95% CI: 2.70-5.17) in 2020. Following BSP implementation, acute CRC presentations were reduced by 61% (IRR 0.39, 95% CI: 0.31-0.49, p < 0.001). Post-BSP patients were less likely to present with metastatic disease (21% vs. 35%, p = 0.010) or require palliative management on admission (9.3% vs. 19%, p = 0.023). One-year mortality was significantly lower following the BSP (28% vs. 40%, p = 0.037). CONCLUSION: Implementation of the BSP was associated with a substantial reduction in the incidence of acute CRC presentations and evidence of earlier disease at emergency diagnosis. These findings support the effectiveness of organised bowel screening in reducing the presentation of advanced CRC.