Emergency Department Use Prior to Cancer Diagnosis and Mortality.

Importance: The emergency department (ED) is a common yet understudied route to cancer diagnosis. It has been reported that over 1 in 3 patients in Ontario, Canada, used the ED prior to cancer diagnosis. Objective: To examine the association between ED use in the 90 days prior to cancer diagnosis and subsequent mortality. Design, Setting, and Participants: This matched, retrospective, population-based cohort study used administrative health data from Ontario, Canada. Adults (aged ≥18 years) diagnosed with cancer between January 1, 2014, and December 31, 2021, were included. Patients were followed from index diagnosis until death, 7 years, or end of the study (March 31, 2024). To create the cohort, patients with and without ED use prior to diagnosis were matched 1:1 on sex and year of diagnosis, and then were propensity score matched. Exposure: Any ED visit in the 90 days prior to diagnosis. Main Outcomes and Measures: The primary outcome was all-cause mortality after cancer diagnosis. A Cox proportional hazards regression model was used to estimate mortality risk. Interaction with time using restricted cubic splines was included to model the time-varying relationship between ED use and mortality. Results were stratified by hospitalization on the ED visit vs discharge from the ED. Results: A total of 205 060 (89.3%) patients with ED use prior to cancer diagnosis were matched to patients without ED use prior to diagnosis. Of the 410 120 total patients included, the mean (SD) age was 67.4 (15.0) years, and 106 681 (52.0%) per group were male. Overall mortality was 49.7%: 61.7% in patients with an ED visit vs 37.8% in patients without an ED visit. Patients with ED use prior to diagnosis had statistically significantly higher risk of mortality compared with those without ED use, which decreased with time but persisted through the 7-year follow-up (hazard ratio [HR] at 30 days: 4.49 [95% CI, 4.40-4.58]; HR at 1 year: 1.85 [95% CI, 1.82-1.88]; HR at 3 years: 1.48 [95% CI, 1.46-1.50]; HR at 7 years: 1.05 [95% CI, 1.01-1.09]). In stratified analysis, the increased hazard of death among patients with ED use was even higher among those admitted to the hospital vs the overall model, which persisted over the follow-up time (HR at 30 days: 5.83 [95% CI, 5.69-5.99]; HR at 1 year: 2.23 [95% CI, 2.19-2.27]; HR at 3 years: 1.74 [95% CI, 1.70-1.77]; HR at 7 years: 1.30 [95% CI, 1.23-1.37]). Patients discharged from the ED also had a greater hazard of mortality vs those without ED use, which persisted to 3 years of follow-up (HR at 30 days: 2.68 [95% CI, 2.59-2.77]; HR at 1 year: 1.81 [95% CI, 1.76-1.86]; HR at 3 years: 1.38 [95% CI, 1.34-1.41]; HR at 7 years: 1.03 [95% CI, 0.98-1.10]). Conclusions and Relevance: In this cohort study of patients diagnosed with cancer, those with ED use prior to cancer diagnosis had a higher hazard of mortality. This finding highlights the need for (1) established systems of care to ensure timely cancer workup for patients in the ED with suspected cancer and (2) health care system improvements to enhance early cancer detection and management to reduce reliance on emergency care for initial cancer presentations.