Abstract
BACKGROUND: Adults with intellectual or developmental disability (IDD) are at higher risk for incomplete cancer staging. AIM: To compare unknown stage data between those with and without IDD. MATERIALS AND METHODS: We used the Ontario Cancer Registry linked to administrative health data between 2007 and 2019. RESULTS: Adults with IDD diagnosed with breast, colorectal, and lung cancer were 1.94 (95% CI 1.52-2.47), 1.90 (95% CI 1.63-2.21), and 2.17 (95% CI 1.86-2.54) times more likely to have unknown cancer stage at diagnosis, relative to those without IDD. DISCUSSION: The absence of stage data has person-level and population-level implications. At the individual level, if stage data are not simply missing from the registry but reflect incomplete or absent diagnostic or staging procedures, this may represent barriers for adults with IDD in receiving curative treatment. At the population level, research using inaccurate or incomplete stage data may lead to unrepresentative health and social system policy decisions. CONCLUSION: A better understanding of the cancer diagnostic interval for adults with IDD is needed to develop interventions.