Date

October 2010

Document Type

Thesis

Degree Name

M.P.H.

Department

Dept. of Public Health and Preventive Medicine

Institution

Oregon Health & Science University

Abstract

Background: Endoscopic ultrasound (EUS) is the most accurate imaging modality used in the staging of rectal cancer, but its impact on clinical outcomes of patients with rectal cancer remains unclear. The aim of this study was to evaluate the receipt of EUS and its association with overall survival in a cohort of patients with rectal cancer. Methods: All patients over the age of 65 who were diagnosed with rectal cancer between January 1997 and December 2003 in the Surveillance, Epidemiology and End Results (SEER)-Medicare linked database were identified, with follow-up data through 2006, and demographic, cancer-specific, and EUS procedural information were extracted. The primary goal of this analysis was to examine whether patients who received EUS evaluations experienced differences in survival rates than patients who did not receive EUS. Additionally, adjusted Hazard Ratios (HR) were estimated using Cox proportional hazards regression, to examine rectal cancer specific survival among EUS and non-EUS groups. A secondary analysis was performed to examine the factors that influenced receipt of EUS. A multivariate logistic regression model was fit to examine the association, adjusting for demographic and clinical characteristics. Results: A Total of 6,294 patients with adenocarcinoma of the rectum were identified from the SEER-Medicare linked database that fulfilled the inclusion and exclusion criteria. Their median age was 76 years (IQR 71-82 years), 3121 (49.6%) were men, and 5598 (88.9%) were white. The stages of rectal cancer diagnoses were local (58.2%) and regional (41.8%). Overall, 801 of 6,294 (12.7%) patients underwent EUS for evaluation and staging of rectal cancer. Patients without comorbidities were no more likely than patients with comorbidity scores ≥ 1 to receive EUS (13.6% vs. 11.9% p=0.05). Curative surgery, chemotherapy and radiation therapy were also performed more frequently in the patients who underwent EUS. Receipt of EUS was associated with a reduced risk of death (adjusted relative ratio, 0.68; 95% CI, 0.59-0.77; p < 0.001). Additionally, in the multivariate model, age older than 75 years, late tumor stage, and a comorbidity score > 0 were significant predictors of poor survival. Conclusions: After adjusting for patient factors and clinical characteristics, receipt of EUS is associated with improved survival in rectal cancer patients compared to non-receipt of EUS. The improved benefit is likely a marker of access to stage-appropriate management such as neo-adjuvant therapy and surgical resection.

Identifier

doi:10.6083/M4DF6P68

School

School of Medicine

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