Abstract

Background: People with an intellectual disability (ID) are at increased risk of bowel cancer. However, evidence on their presenting symptoms, diagnostic pathways, treatments and survival remains limited. Methods: A matched cohort study was conducted using linked primary care (Clinical Practice Research Datalink), hospital, cancer, and mortality records. Outcomes included symptoms associated with bowel cancer, faecal immunochemical or faecal occult blood (FIT/FOB) testing, urgent suspected cancer (USC) referral, endoscopy, surgery, systemic anticancer therapy (SACT), and bowel cancer-specific mortality. Adjusted incidence rate ratios (aIRRs), risk ratios (aRRs), and hazard ratios (aHRs) were estimated using Poisson, modified Poisson and Cox regression. Results: A total of 111,034 individuals with an ID were matched to 1,964,420 comparators. ID was associated with increased risk of bowel cancer (aHR 1.30, 1.18-1.44), particularly before age 50 years (aRR 2.19, 1.68-2.85). People with an ID presented more frequently with symptoms associated with bowel cancer (aIRR 2.59, 2.53-2.65) but, following such symptoms, were less likely to undergo FIT/FOB testing (aRR 0.74, 0.67-0.83), USC referral (aRR 0.57, 0.52-0.62), endoscopy (aRR 0.45, 0.42-0.49), or receive a diagnosis within 56 days (aRR 0.52, 0.41-0.67). They were also less likely to be diagnosed via screening (aRR 0.27, 0.14-0.50) or USC referral (aRR 0.62, 0.50-0.76), and more likely to be diagnosed via emergency presentation (aRR 1.76, 1.52-2.02), on the date of death (aRR 5.08, 2.92-8.84), or with stage IV disease (aRR 1.25, 1.01-1.56). ID was associated with similar proportions receiving curative surgery for stage I-III disease (aRR 0.98, 0.79-1.19), but markedly lower proportions receiving SACT for stage IV (aRR 0.15, 0.05-0.46), and higher bowel cancer-specific mortality across all stages (aHR 2.00, 1.71-2.33). Conclusions: People with an ID experience worse outcomes across nearly all stages of the bowel cancer care pathway, including referral, investigation, treatment and survival. Earlier screening may be justified given the elevated risk in those under age 50 years.