Abstract 864: Association between emergency department (ED) involvement in cancer diagnosis and survival across cancer types in the Medicare population.

Abstract Background: A substantial proportion of cancers are diagnosed following an emergency presentation, a pathway consistently associated with advanced stage at diagnosis, poorer survival, and worse patient experience. We aimed to quantify the association between ED involvement in the diagnosis of cancer and overall survival across different cancer types in the Medicare population. Methods: We conducted a retrospective cohort study of SEER-Medicare beneficiaries diagnosed with invasive cancer between 2010 and 2020 and followed for mortality until 12/31/2020, defining the earliest cancer-related claim as the index date. We excluded beneficiaries without at least 12 months of continuous Medicare Parts A/B/D enrollment before and 1 month after the index date or with a prior cancer diagnosis within one year. Patients with an ED visit within 30 days before the index date were classified as having ED involvement in their diagnosis. Overall survival was evaluated using 17 independent multivariate Cox proportional hazards models, each corresponding to a cancer grouping defined according to SEER major cancer sites with available AJCC staging data (breast, prostate, lung, colorectal, bladder/urothelial tract, uterine, kidney, lymphoma, pancreatic, oral, liver, stomach, ovarian, esophageal, cervical, anal). Covariates included age, sex, race/ethnicity, dual eligibility status, Charlson Comorbidity Index, year of diagnosis, and tumor stage. This analysis did not adjust for some potential confounders including differences in duration of symptoms, performance status, and therapy access or initiation which were not captured in the dataset. Results: Among 818,120 beneficiaries newly diagnosed with cancer (mean age 74.4 years), 26.4% had ED involvement in their diagnosis. The proportion with ED involvement increased with advancing stage across all cancer types (stage I: 13.8%, II: 26.3%, III: 23.7%, IV: 47.3%) and varied across cancer types, ranging from 6.1% for breast cancer to 53.4% for pancreatic cancer. Mortality during the study period was 44.4% among patients with ED involvement versus 19% among those without, with 46% of cancer deaths following ED involvement. ED involvement was associated with significantly higher mortality across nearly all cancer types, except cervical cancer (HR 0.81; 95% CI 0.28-2.37), ranging from pancreatic (1.61; 1.54-1.67) and colorectal (1.88; 1.84-1.93) to esophageal (3.86; 2.25-6.62) and bladder (4.08; 3.23-5.18). Conclusion: ED involvement was associated with a significant fraction of overall mortality in patients with cancer and was a strong independent predictor of mortality after adjustment for patient factors including socioeconomics, comorbidities, and cancer stage at diagnosis. These findings highlight the need for strategies that promote earlier, non-emergency diagnostic pathways and structured follow-up. Citation Format: Shannon Heitkamp, Eric Olsen, Ali Tafazzoli, Bethany Houpt, Olivia Hunt, Anuraag R. Kansal, A Mark Fendrick, Eric Klein. Association between emergency department (ED) involvement in cancer diagnosis and survival across cancer types in the Medicare population abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 864.