Comorbidities, Socioeconomic Status, and Colorectal Cancer Diagnostic Route.

Importance: Reducing emergency cancer diagnoses is a public health priority, as they are associated with worse outcomes. Preexisting chronic conditions can influence screening participation and emergency cancer diagnosis; however, evidence is mixed, and data from Southern Europe are scant. Objective: To examine variations in the likelihood of colorectal cancer (CRC) diagnosis following an emergency presentation (EP) or screening by patient comorbidity status and socioeconomic characteristics and to investigate the association of patient characteristics, diagnostic route, and comorbidity status with short-term CRC mortality. Design, Setting, and Participants: This population-based cohort study used linked cancer registry data and administrative health data from the Agency for Health Protection of Milan, Italy, for CRC cases diagnosed between July 1, 2014, and December 31, 2020, in the provinces of Milan and Lodi, Italy. Data were analyzed from January 1 to October 1, 2024. Exposures: Comorbidity status (number of comorbidities, specific preexisting comorbidities) and socioeconomic characteristics (including age, sex, and deprivation index). Main Outcomes and Measures: The primary outcomes were routes to cancer diagnosis (screening, emergency presentation, or inpatient or outpatient visits), cancer stage at diagnosis, and short-term mortality (30 days and 1 year). Multivariable and multinomial logistic regression models were used to estimate odds ratios (ORs) adjusted for socioeconomic and comorbidity factors. Results: Among 14 457 patients, 10 750 (74.4%) had colon cancer and 3707 (25.6%) had rectal cancer. The route to diagnosis was reconstructed for 10 514 patients with colon cancer (97.8%; median age, 73.1 years [IQR, 66-82 years]; 5563 [52.9%] male) and 3635 with rectal cancer (98.1%; median age, 70.3 years [IQR, 62-80 years]; 2079 [57.2%] male). Of those, 4697 patients with colon cancer (44.6%) and 2094 with rectal cancer (57.6%) had comorbidities, emergency diagnosis occurred in 3738 colon (35.6%) and 823 rectal (22.6%) cancer cases, and diagnosis while screening occurred in 881 colon (8.4%) and 347 rectal (9.5%) cancer cases. Emergency diagnosis was associated with having cerebrovascular (adjusted OR [AOR], 1.50; 95% CI, 1.23-1.82) and neurological (AOR, 1.67; 95% CI, 1.33-2.09) diseases or having 3 or more comorbidities compared with having none (AOR, 1.78; 95% CI, 1.47-2.16) among patients with colon cancer. Having 3 or more vs no comorbidities was associated with lower odds of screening-detected colon cancer (AOR, 0.64; 95% CI, 0.45-0.91). Higher 30-day (AOR, 4.84; 95% CI, 2.81-8.33) and 1-year (AOR, 2.77; 95% CI, 2.17- 3.53) mortality was associated with emergency presentation. The COVID-19 period was associated with higher odds of emergency diagnoses compared with the prepandemic period (AOR, 1.32; 95% CI, 1.15-1.52). Conclusions and Relevance: In this cohort study of patients with CRC in Italy, emergency diagnosis occurred for more than 1 in 3 patients with colon cancer. Having 3 or more comorbidities was associated with a lower likelihood of screening detection and higher odds of emergency diagnosis. Tailored interventions are needed to facilitate screening, to reduce emergency cancer diagnoses, and to improve outcomes for patients with chronic conditions.