Colonoscopy Associated With Drop in New Colorectal Cancer

The increasing use of colonoscopy to screen for colorectal cancer (CRC) corresponds with a decline in colorectal cancer incidence among those aged 50 years and older, according to a study published in the November issue of Gastroenterology.

The study, which uses data on 2 million patients collected from 1993 to 2009, also shows that CRC rates appear to be rising in younger adults.

Parvathi A. Myer, MD, from the Division of Gastroenterology and Hepatology, Stanford University School of Medicine, California, and colleagues used surgical resection for CRC as a proxy for CRC incidence, as most people diagnosed with CRC undergo at least a single surgery.

Using data from the Nationwide Inpatient Sample, the largest inpatient database in the United States, the researchers looked at resections in adults and analyzed them according to 4 age groups: 18- to 39-year-olds (ie, those younger than the recommended age for routine screening); 40- to 49-year-olds, who may be screened because of a family history of CRC; 50- to 75-year-olds, who are advised to have a baseline colonoscopy; and those 76 years old and older, who are not recommended for screening by the US Preventive Services Task Force.

The authors found a decline in CRC resections during the study when they looked at all adults. The rate of resections fell from 71.1 per 100,000 people in 1993 (95% confidence interval [CI], 65.9 - 76.2) to 47.3 per 100,000 people in 2009 (95% CI, 43.4 - 51.2). The largest decrease occurred after 2000, the research shows (P < .001). Although resection rates fell 0.9% annually (95% CI, 0.1% - 1.7% decline) from 1993 to 2000, the rate fell by 3.4% per year (95% CI, 2.8% - 3.9% decease) from 2000 to 2009.

"Widespread colonoscopy screening may actually be having an impact in the risk of colon cancer at the level of the general population," Uri Ladabaum, MD, associate professor of gastroenterology and hepatology and senior investigator for the study, said in a university news release. Several groups, including the American Cancer Society, recommend CRC screening at age 50 years for people without an increased risk for CRC. Medicare began covering colonoscopies for people of average risk in 2001, as did many insurers.

The authors say the study shows the positive effect of colonoscopy and its ability to reach the upper (proximal) portion of the colon compared with other screening methods, including fecal occult blood testing (FOBT) and sigmoidoscopy, which examines only the lower colorectum. Some recent studies have questioned the efficacy of colonoscopy in decreasing both CRC incidence and mortality.

FOBT, Sigmoidoscopy Cannot Explain Trend

"It is unlikely that FOBT or sigmoidoscopy use explain the trend in proximal CRC resection rates because FOBT uptake rates have been relatively flat over time, and have decreased in the past decade, whereas sigmoidoscopy use has decreased substantially," the authors write.

The data show a decline in the rate of proximal resection that corresponds to the increase in colonoscopy, the authors write. The rate fell from 30.0 per 100,000 persons (95% CI, 27.4 - 32.5) to 22.7 per 100,000 persons (95% CI, 20.6 - 24.7) from 1993 to 2009. The largest annual decrease occurred later, from 2002 to 2009, when the annual resection rate fell by 3.1% (95% CI, 2.3% - 4.0%; P < .001).

Distal resections also declined in correspondence with the increase in colonoscopy. The rate of distal CRC resections fell 1.2% a year (95% CI, 0.1% - 2.3%) from 1993 to 1999, but from 1999 to 2009, the rate of resections fell 3.8% annually (95% CI, 3.3% - 4.3%; P < .001).

Resection rates for CRC for adults aged 50 years and older followed the overall trend in decline, but rates increased from 1993 to 2009 in younger groups. The rate increased 1.3% (95% CI, 0.8% - 1.8%) per year among those aged 40 to 49 years and by 2.4% annually (95% CI, 1.7% - 3.1%) for people aged 18 to 39 years.

"These trends probably reflect an increase in the prevalence of CRC risk factors and the absence of screening in these younger adults," the authors write.

The rate of resection fell fastest among those aged 76 years and older, with distal CRC falling 3.0% annually (95% CI, 1.9% - 4.1% decrease) from 1993 to 2000 and 5.8% (95% CI, 5.0% - 6.6% decline) after 2000 (P < .001). Proximal CRC fell 1.1% per year (95% CI, 0.3% - 2.0% decrease) from 1993 to 2001 in this age group, and then by 3.6% per year (95% CI, 2.8% - 4.4% decline; P <.001) from 2001 to 2009.

The decline in resections among the oldest group, for whom colonoscopy is not recommended, could mean that colonoscopies and accompanying polypectomy at a younger age were having a late-life effect, Dr. Ladabaum suggested in the news release.

Study limitations include a lack of data regarding CRC risk factors and medication use in the population investigated, both of which may have influenced CRC risk (eg, use of nonsteroidal anti-inflammatory drugs or history of tobacco use). In addition, conclusions cannot be drawn about causality, and there was no adjustment made for race or ethnicity.

The study was supported by the National Institutes of Health. The authors have disclosed no relevant financial relationships.

Gastroenterology. 2012;143:1227-1236. Abstract

 

By Jenni Laidman, Medscape Medical News
Reviewed / Posted by: Scott W. Yates, MD, MBA, MS, FACP

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