Subsite-specific colorectal cancer risk in the colorectal endoscopy era.

BACKGROUND

Colorectal endoscopy (sigmoidoscopy and colonoscopy) is thought to reduce colorectal cancer (CRC) risk. Since the 1980s, its use has increased in the United States, which may be a reason for decreasing CRC incidence rates.

OBJECTIVE

To investigate the plausibility of a contribution of colorectal endoscopy use to the decrease in CRC risk.

DESIGN

Descriptive analysis of temporal trends.

SETTING

U.S. population from 1978 to 2007.

MAIN OUTCOME MEASUREMENTS

Using incidence data from the Surveillance, Epidemiology and End Results Program, we assessed the subsite-specific cumulative risk of CRC developing until age 79 years.

RESULTS

The cumulative risk of proximal CRC remained relatively stable over the observation period, varying between 2.09% (95% CI, 2.06%-2.11%) and 2.66% (95% CI,2.62%-2.69%) for men and between 1.90% (95% CI, 1.88%-1.93%) and 2.24% (95% CI, 2.21%-2.27%) for women. By contrast, the cumulative risk of distal CRC decreased from 4.68% (95% CI, 4.64%-4.73%) to 3.03% (95% CI, 3.00%-3.06%) for men and from 3.15% (95% CI, 3.11%-3.18%) to 1.93% (95% CI, 1.91%-1.95%) for women, which was largely attributable to the reduced cumulative risk of cancer in the sigmoid colon. The observed pattern was restricted to the population aged 50 to 79 years, whereas the magnitude of the decrease was greater for older age groups and similar across stages.

LIMITATIONS

The study is based on aggregated registry data only; therefore, no inferences about causal effects can be drawn.

CONCLUSIONS

The results show a major reduction of CRC risk, particularly in the sigmoid colon. Increased use of colorectal endoscopy in the population aged 50 years and older along with environmental factors may have contributed to the decreasing risk.