Kelsea Shoop


December 2009

Document Type


Degree Name



Dept. of Public Health and Preventive Medicine


Oregon Health & Science University


BACKGROUND: Colorectal cancer (CRC) is the third most common cancer type in the United States and the third-leading cause of deaths among both men and women. The five year survival in colorectal cancer stage II is approximately 80% and in stage III reduced to 50% (1). Colon cancer is also one of the most curable types of cancer if it is diagnosed early. METHODS: This study is a historic cohort of anonymized secondary data and examines the relationship between increasing age and cancer directed therapy for colon cancer stages I-III, within the Medicare population. The purchased SEER Medicare linked sample provided patients who had a colon cancer diagnosis, identified by ICD-9 diagnosis code, from 2000-2005 with follow-up data through 2005. Patients were categorized by age into five-year increments starting with age 65. The primary goal of this analysis was to examine whether older patients receive less cancer directed therapy than younger patients, stratified by cancer stage. Two multivariate logistic regression models were fit to examine the associations. The first examined the association between older age and receipt of cancer directed therapy, adjusting for demographics and clinical characteristics. The second model looked at the association between older age and the number of lymph nodes examined during surgery. Additionally, adjusted hazard ratios (HR) were estimated using Cox proportional hazards regression, to examine colon cancer specific survival among age groups. RESULTS: Subjects aged 70-74 were significantly (OR=0.21, 95% CI: 0.13-0.52) less likely to receive cancer directed therapy compared to those aged 65-69. This result was seen at all older age categories. Individuals over the age of 90 were 1.82 times more likely to have inadequate surgery (OR=1.82 95% CI: 1.57-2.21). Interestingly, Blacks (OR=1.16 95% CI: 1.06-1.27), Asians (OR=1.14 95% CI: 1.01-1.30), and Hispanics (OR=1.64 95% CI: 1.35-2.00) were all more likely to have inadequate surgery than Whites. Age was a significant predictor of poor colon cancer survival in all subjects. The largest HR was seen among subjects who did not receive cancer directed therapy. CONCLUSIONS: After adjusting for patient factors and clinical characteristics elderly patients were significantly more likely to receive less cancer directed therapy and receive inadequate resection. Increased age was strongly associated with colon cancer mortality. However, among subjects who received cancer directed therapy stage of disease was more highly associated with mortality than age. While subjects who did not receive cancer directed therapy were much more likely to die from age than their disease.




School of Medicine



To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.