Shorter Colonoscopies Linked to Higher Cancer Intervals

Colonoscopies that take longer are linked to lower cancer rates, according to findings published in Gastroenterology.

Researchers from the Veterans Affairs Research Communications analyzed more than 75,000 colonoscopy records to determine if the length of the colonoscopy was linked to undetected adenomas. The researchers noted that withdrawal times and adenoma detection rates were common indicators for screening colonoscopy and adenomas could increase the risk for interval colorectal cancer.

The records were acquired from colonoscopies performed between 2004 and 2009 by 51 gastroenterologists in Minneapolis and St. Paul, Minnesota. The colonoscopy records were gathered from the electronic state cancer registry (the Minnesota Cancer Surveillance System) and analyzed to identify interval cancers that were diagnosed within 5.5 years after the screening examination.

“Our results support the use of withdrawal time as a quality indicator, as recommended by current guidelines,” lead author Dr. Aasma Shaukat, with the Minneapolis VA Health Care System and the University of Minnesota, explained in a press release.

The withdrawal time is a specific part of the colonoscopy process wherein the thin tube affixed with a camera is slowly pulled out of the patient’s colon. The doctor then inspects the colon lining for any anomalies or polyps. The polyps are removed with the snipping tool — also attached to the camera tube – and sent for biopsy, where they may grow into cancer within a few years. “Normal” colonoscopy, as dictated by current guidelines, is one in which there are no findings of cancerous or pre-cancerous growths and the doctor does not have to remove any tissue for biopsy. The withdrawal time for “normal” colonoscopy should be at least six minutes.

The researchers found that the average time for withdrawals in the colonoscopies was about 8.6 minutes, but there were 10% of doctors who had individual averages of less than six minutes. The researchers then examined those doctors’ states’ cancer registries and found patients who had been screened during the study observation period.

The patients examined by doctors with shorter withdrawal averages (under six minutes) were more than twice as likely to have cancer. Additionally, there did not appear to be any extra reduction of risk when withdrawal times were greater than 8 minutes.

“We need to understand the quality indicators better, define thresholds, and be able to adjust them to the particular patient population and underlying risk,” concluded Shaukat. “Until there are uniform methods for data collection, adjustment, and collection, the numbers don’t mean much. We might be comparing apples to oranges.”

Previous research has shown there was a link between colonoscopy withdrawal times and patient outcomes, but this study added strong evidence to support clinical guidelines outlining this part of the procedure.