Date of Award

January 2026

Document Type

Open Access Thesis

Degree Name

Medical Doctor (MD)

Department

Medicine

First Advisor

Thiruvengadam Muniraj

Abstract

AbstractBackground/Scientific Premise: Colon cancer represents a significant public health burden in the United States, ranking as the third most common and second deadliest cancer. Timely surgical resection is critical for optimal survival in non-metastatic disease, yet persistent racial, insurance, and geographic disparities in access to care may contribute to treatment delays. While treatment delay has been established as a critical quality metric, regional variation in surgical delays for colon cancer and how patient-level disparities manifest across different U.S. regions remain poorly understood. Understanding these geographic patterns is essential, as healthcare systems, patient populations, access barriers, and state-level policies differ substantially across regions. Research Aims: This study aimed to assess regional variation in surgical treatment delays (>8 weeks from diagnosis) for Stage I–III colon cancer across the nine U.S. Census Divisions and to determine how racial, insurance, and geographic disparities in treatment delay manifest and evolve across regions from 2004 to 2021. Hypothesis: We hypothesized that racial, insurance, and urban/rural disparities in surgical treatment delay would vary significantly across U.S. Census Divisions, and that these geographic disparities would evolve over time, with certain regions showing widening gaps in access to timely surgical care. Methods/Approach: We conducted a retrospective cohort study using data from the National Cancer Database (2004-2021), analyzing 664,312 patients aged ≥40 years diagnosed with Stage I-III colon cancer who underwent surgical resection as first-course treatment at Commission on Cancer-accredited facilities. The primary outcome was surgical delay >8 weeks from diagnosis to surgery. Multivariable logistic regression models with interaction terms assessed regional variation in disparities by race, insurance status, and urban/rural residence. Adjusted predicted probabilities and odds ratios with 95% confidence intervals were calculated. Results: Overall, 48,579 patients (7.3%) experienced surgical delays >8 weeks, increasing from 4.5% in 2004 to 12.2% in 2021 (adjusted odds ratio [aOR] 2.77; 95% CI, 2.61–2.94). Compared with White patients, Black (aOR 1.34; 95% CI, 1.31−1.38), American Indian/Alaska Native/Aleut/Eskimo (aOR 1.24; 95% CI, 1.06−1.45), and Asian American (aOR 1.06; 95% CI, 1.01-1.12) patients had significantly higher odds of delay. Medicaid patients (aOR 1.19; 95% CI, 1.11−1.28) and those with Other/Unknown/Government insurance (aOR 1.16; 95% CI, 1.07−1.26) also faced increased odds compared to uninsured patients. Significant regional variation was identified (p<0.001 for all interactions), with the largest Black–White disparity in West North Central (9.0% vs 4.9% predicted probability) and smallest in East South Central (5.2% vs 4.6%). East South Central (aOR 0.60) and West North Central (aOR 0.67) regions had lower odds of delay compared to New England, while the Pacific region demonstrated the steepest increase in delays over time (4.5% in 2004 to 14.4% in 2021). Statement of Scientific Impact and Relevance for Communities of Interest: This study identifies substantial and growing regional inequities in timely access to curative colon cancer surgery across the United States. The near tripling of surgical delays over 17 years, coupled with persistent and geographically heterogeneous racial and insurance-based disparities, represents a critical patient safety and equity concern. These findings have direct implications for the 150,000 Americans diagnosed with colon cancer annually and the healthcare systems charged with their care. For patients, delays in surgical treatment can lead to disease progression, treatment complications, psychological distress, and reduced survival. The identification of high-risk populations (Black, American Indian/Alaska Native, Medicaid beneficiaries) and high-disparity regions (West North Central, Pacific) provides actionable targets for intervention. For healthcare systems and policymakers, these results underscore the urgent need for targeted quality improvement initiatives, enhanced surgical capacity planning, culturally tailored patient navigation programs, and policy reforms addressing insurance-based access barriers. By illuminating the specific geographic and demographic patterns of inequity, this research provides an evidence base for resource allocation decisions and system-level interventions to ensure all colon cancer patients receive timely, guideline-concordant surgical care regardless of race, insurance status, or geographic location.

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