Date of Completion


Embargo Period



Anderson Joseph, MD; Jane A. Ungemack, Dr.P.H

Field of Study

Public Health


Master of Public Health

Open Access

Campus Access


Colorectal cancer is the third most common cancer and is the second cause of death from cancer. Recently, research suggests that there are differences in the incidence and mortality for cancers originating from the different locations of large intestine. Proximal cancers lag behind in terms of reduction in mortality rates, improved survival, and reduction in incidence. We conducted a study to understand the clinicopathological differences between proximal, distal, and rectal cancers and identify patients with increased likelihood for proximal cancer (cross-sectional data from the SEER from 1973 to 2007 from 17 registries (n=505,141)). There were 204,168 cases of proximal tumors (40.4%), 146,011 cases of distal tumors (28.9%), and 154,962 cases of rectal tumors (30.7%). The proportion of proximal cancers increased from 35.6% (1973-1977) to 42.2% (2003-2007). Blacks and whites had the highest proportions of proximal tumors (46.1% and 41.1%, respectively) American Indians and Hispanics had (37.2% and 36.4%, respectively) while Asians had 30.1% Female and older individuals (>60) had significantly higher proximal tumors than males and younger cases. Proximal tumors were associated with advanced tumor grade and later stage (P<0.001). Multivariate Logistic Regression showed that older age (>60) and African Americans, females, and year of diagnosis were all independently associated with an increased likelihood of proximal tumors. All remained significant in sub-analyses comparing the rural versus urban populations, and SEER 9 registries. This study helps to identify the subgroup of patients who have a higher likelihood of proximal cancers, and for whom efforts to enhance colonoscopy screening rates are needed.

Major Advisor

Helen Swede, Ph.D.