D. Yu1,2, M. Stem2, J. Taylor2, S. Chen2, B. Safar2, S. Fang2, S. Gearheart2, J. Efron2 1Queen’s University,General Surgery,Kingston, ONTARIO, Canada 2The Johns Hopkins University School Of Medicine,Colorectal Surgery,Baltimore, MD, USA
Introduction:
Recent studies report a shift in the anatomical site of origin of colon cancer from the distal to the proximal colon. The objective of this study was to assess sub-site specific differences of colon adenocarcinomas with respect to patient and tumor characteristics, treatment trends, and overall survival (OS).
Methods:
This study was conducted using data from the National Cancer Database (2004 – 2015). Adult patients > 18 years old diagnosed with stage I to IV colon adenocarcinoma were stratified by primary site of cancer (right, transverse, left, or sigmoid). Primary outcome of interest was 5-year OS analyzed using Kaplan-Meier survival curves and Cox proportional hazard models.
Results:
A total of 642,983 cases were included [right: 330,872 (51.46%), transverse: 66,621 (10.36%), left: 63,947 (10.36%), sigmoid: 181,543 (28.23%)]. A small but significant increase in diagnosis from 2004 to 2015 was found in right-sided and transverse colon cancers (right: 8.04% to 8.57%, transverse: 7.80% to 8.99%, p-value <0.001 for both). Right and transverse colon cancer patients tended to be female, older, have higher frequencies of poorly differentiated tumors (right: 20.99%, transverse 18.82%, left: 14.27%, sigmoid 11.68%, p-value <0.001), and tumors > 5cm (40.51%, 35.76%, 33.77%, 29.79%, respectively, p-value <0.001). When stratified by stage, sigmoid cancer patients were more likely to receive multimodal therapy compared to other sub-sites across all stages. In the unadjusted analysis, right and transverse colon cancers had the worst 5-year OS (53.30%, 54.01%, 55.93%, 58.39%, respectively, p-value <0.001). Similar trends persisted when stratified by stage (FIGURE). In the adjusted Cox analysis, right, transverse, and left colon cancers all had significantly increased risk of mortality in comparison to sigmoid cancer when all stages were combined (sigmoid ref: HR: 1.10, 95% CI 1.08-1.12, HR 1.16, 95% CI 1.13-1.19, HR 1.12, 95% CI 1.09-1.15, p-value <0.001 for all). When stratified by stage, right and transverse colon cancers had the greatest risk of death in stages III and IV (sigmoid ref, stage III: transverse HR 1.21, 95% CI 1.16-1.26, p-value <0.001, stage IV: right HR 1.28, 95% CI 1.24-1.31, p-value <0.001)
Conclusion:
Right-sided and transverse cancers show an increasing trend over the study period. These patients tended to be female, older, have higher frequency of poor differentiation, and larger tumors. 5-year OS was worst in transverse cancers for all stages combined.
