Proximal colon cancers are more likely to present with advanced stage than distal cancers; however, previous reports conflict regarding the independent prognostic significance of tumor location on survival. We examined survival by colon cancer subsite location by use of data from the California Cancer Registry.
An analysis of colon cancer cases from 1994 to 2004 was conducted, with follow-up through 2006. Colon subsite location was defined as proximal colon (cecum, ascending colon, hepatic flexure), transverse colon, descending colon (splenic flexure, descending colon), and sigmoid colon. Subsite-specific survival analyses were conducted with use of the Kaplan-Meier method and Cox proportional hazards ratios.
A total of 82,926 colon cancer cases were identified, including 40,078 proximal (48%), 8,023 transverse (10%), 8,657 descending (10%), and 26,168 sigmoid cancers (32%). A larger proportion of sigmoid cancers (30.5%) presented as Stage I compared with proximal (18.5%), transverse (16.8%), or descending colon cancers (20.1%). Proximal cancers had the greater proportion with high tumor grade (27%), and had a greater mean number of lymph nodes examined. There were no differences in treatment rendered when each colon subsite was stratified by stage. After adjustment for stage, grade, treatment, lymph node examination, and other relevant clinical variables, sigmoid cancers had decreased colorectal cancer-specific mortality compared with proximal tumors (hazards ratio = 0.88; 95% confidence interval, 0.85–0.92).
In this analysis, sigmoid colon cancers were observed to have earlier stage, lower tumor grade, and independently decreased colorectal cancer-specific mortality compared with proximal tumors.
1 College of Osteopathic Medicine of the Pacific, Western University of Health Sciences, Pomona, California
2 Genetic Epidemiology Research Institute and Department of Epidemiology, School of Medicine, University of California, Irvine, California
3 Division of Colon and Rectal Surgery, Department of Surgery, School of Medicine, University of California, Irvine, California
4 Chao Family Comprehensive Cancer Center and Division of Hematology/Oncology, Department of Medicine, School of Medicine, University of California, Irvine, California.
Supported by Department of Epidemiology, Division of Hematology/Oncology, Department of Medicine, University of California, Irvine, California.
Disclaimer: The collection of cancer incidence data used in this study under Subcontract 050N-8707-S1527 with the Public Health Institute, State of California, was supported by the California Department of Health Services as part of the statewide cancer reporting program mandated by California Health and Safety Code Sections 103875 and 103885, the National Cancer Institute’s Surveillance, Epidemiology and End Results Program, and the Centers for Disease Control and Prevention National Program of Cancer Registries. The ideas and opinions expressed herein are those of the authors and endorsement by the State of California, Department of Health Services, the National Cancer Institute, the Centers for Disease Control and Prevention, and/or the Genetic Epidemiology Research Institute of the University of California, Irvine, is not intended nor should be inferred.
Address of correspondence: Jason A. Zell, Department of Epidemiology, School of Medicine, University of California, Irvine, 224 Irvine Hall, Irvine, California 92697. E-mail: firstname.lastname@example.org