Comorbid conditions delay diagnosis of colorectal cancer: a cohort study using electronic primary care records

Background: Pre-existing non-cancer conditions may complicate and delay colorectal cancer diagnosis. Method: Incident cases (aged >= 40 years, 2007-2009) with colorectal cancer were identified in the Clinical Practice Research Datalink, UK. Diagnostic interval was defined as time from first symptomatic presentation of colorectal cancer to diagnosis. Comorbid conditions were classified as 'competing demands' (unrelated to colorectal cancer) or 'alternative explanations' (sharing symptoms with colorectal cancer). The association between diagnostic interval (log-transformed) and age, gender, consultation rate and number of comorbid conditions was investigated using linear regressions, reported using geometric means. Results: Out of the 4512 patients included, 72.9% had >= 1 competing demand and 31.3% had >= 1 alternative explanation. In the regression model, the numbers of both types of comorbid conditions were independently associated with longer diagnostic interval: a single competing demand delayed diagnosis by 10 days, and four or more by 32 days; and a single alternative explanation by 9 days. For individual conditions, the longest delay was observed for inflammatory bowel disease (26 days; 95% CI 14-39). Conclusions: The burden and nature of comorbidity is associated with delayed diagnosis in colorectal cancer, particularly in patients aged >= 80 years. Effective clinical strategies are needed for shortening diagnostic interval in patients with comorbidity.