Trends in right and left-sided colon cancer

Area of Science:

• Epidemiology
• Gastroenterology
• Oncology

Background:

• Colorectal cancer incidence rates have historically differed between proximal and distal locations.
• Understanding trends in colorectal cancer subsite incidence is crucial for etiological research.

Purpose of the Study:

• To analyze temporal trends in the incidence of proximal versus distal colorectal carcinomas.
• To investigate potential factors influencing observed changes in colorectal cancer subsite distribution.

Main Methods:

• Population-based study of 668 new colorectal carcinoma cases in Rochester, Minnesota, diagnosed between 1940 and 1979.
• Analysis of incidence rates per 100,000 person-years for proximal and distal colorectal lesions over two decades (1940-1959 and 1960-1979).
• Assessment of potential confounding factors including diagnostic criteria and referral patterns.

Main Results:

• Confirmed an increasing ratio of proximal to distal colorectal carcinomas over the study period.
• Observed a rise in proximal lesion incidence (15.1 to 17.3 per 100,000 person-years) and a fall in distal lesion incidence (35.5 to 28.2 per 100,000 person-years).
• Ruled out changes in definitions or referral patterns; improved diagnostics may have influenced proximal lesion incidence.

Conclusions:

• Discrepant incidence trends suggest proximal and distal colon cancers may represent distinct disease entities or arise from different pathogenic pathways.
• No consistent clinical characteristic differences were noted at diagnosis despite changing incidence rates.