Colonoscopy isn't perfect: About six percent of colorectal cancers are missed

March 20, 2014

About 6 percent of colorectal cancers are diagnosed within three to five years after the patient receives a clean colonoscopy report, according to a population-based study by researchers from Huntsman Cancer Institute (HCI) at the University of Utah.

These cancers may have been overlooked at the time of colonoscopy or developed rapidly during the window between colonoscopies and are therefore referred to as "missed" colorectal cancers. The three- to five-year timeframe is well inside the ten years recommended between colonoscopies for screening in the general public, as well as the five years indicated for people at increased risk.

The were published online in the journal Gastroenterology.

"Not only did we find that colonoscopy isn't perfect, we discovered a number of factors associated with these 'missed' cancers," said N. Jewel Samadder, MD, M.Sc., lead author of the study and an HCI investigator. "They tended to appear in patients over the age of 65, patients with a family history of colorectal cancer, and patients in whom polyps were previously found."

The missed cancers were also more likely to appear in the right side of the colon, at the far end of the colonoscope's reach. "Our first thought was that perhaps doctors did not view the entire colon, or that preparation for the procedure was not complete, which would obscure their view," said Samadder. "However, the medical records of the patients with missed cancers showed these problems were seldom present."

The study integrated information about colonoscopies performed at Intermountain Healthcare (IHC) and University of Utah Health Care (UUHC) over the 14-year period between 1995 and 2009. Taken together, the IHC and UUHC systems provide care to more than 85% of Utah's population. The researchers also used the Utah Population Database (UPDB), which combines genealogical, medical, and demographic data with cancer records from the Utah Cancer Registry, which allowed them to count patients who developed colorectal cancer and those who had a family history of the disease while keeping their identities confidential.

While the term 'missed' may indicate that cancer or precancerous polyps were present but not seen, the category also includes cancers that had no visible evidence at the time of colonoscopy but developed rapidly afterward. According to Samadder, "Cancers in the right side are often biologically different than those in other parts of the colon, arising from different types of polyps. These types of polyps are flatter and faster growing, which may explain why they are not seen during colonoscopy as well as how a cancer could develop even when no polyps were visible."

The study showed that in the United States the rate of cancers missed at colonoscopy is only slightly lower than in Germany and Canada where similar studies have been conducted. In the U.S., most colonoscopies are performed by gastroenterologists who receive extensive training in the procedure. Previously, American physicians had assumed that the missed cancer rate would be much lower in the U.S., because many in the foreign health care systems are performed by family physicians, internists, and surgeons who may not be as well trained in the procedure. According to Samadder, physicians and patients need to communicate prior to the procedure to ensure that a complete medical history, accounting for older age, family history of colorectal cancer, and prior history of polyps, is known so extra time and care can be taken during the procedure, especially on the right side of the colon.

Many organizations, such as the American Society of Gastroenterologists (ASGE), now recommend that physicians spend at least 6-10 minutes closely examining the colon lining for polyps during the procedure's withdrawal phase (where they have reached the end of the colon and are beginning to come out).

"This is not entirely a quality of care issue," Samadder said. "Our findings implicate genetic and biological issues associated with having previous polyps and having a of colorectal cancer."

Samadder's research team currently has funding from the American College of Gastroenterology (ACG) to analyze various genetic elements of tumor tissues from missed cancers to search out their molecular signatures and determine how they differ from cancers detected during colonoscopy. "Only by understanding the limitations of colonoscopy," Samadder said, "can we improve its use and ability to detect and thereby reduce the burden of colorectal cancer."

Explore further: Colon cancer screening guidelines may miss 10 percent of colon cancers

Related Stories

Colon cancer screening guidelines may miss 10 percent of colon cancers

October 22, 2013
For people with a family history of adenomas (colon polyps that lead to colon cancer), up to 10 percent of colorectal cancers could be missed when current national screening guidelines are followed. Colorectal cancer is the ...

Too many americans skipping colon cancer screening

March 2, 2012
(HealthDay) -- Approximately one in three U.S. adults between the ages of 50 and 75 who should be screened for colorectal cancer have not been, according to the American Society for Gastrointestinal Endoscopy.

Women can be screened years later than men with 'virtual colonoscopy'

June 10, 2013
A new study has found that women can be screened for colorectal cancer at least five to 10 years later than men when undergoing an initial "virtual colonoscopy." Published early online in CANCER, a peer-reviewed journal of ...

Noninvasive colorectal cancer screening tool shows unprecedented detection rates

March 19, 2014
Results of a clinical trial of Cologuard show unprecedented rates of precancer and cancer detection by a noninvasive test. The detection rates are similar to those reported for colonoscopy. The results were published in the ...

Colonoscopy screening every ten years could prevent 40% of colorectal cancers

September 18, 2013
A study published in the Sept. 19 New England Journal of Medicine provides some of the clearest evidence to date that colonoscopy has advantages over sigmoidoscopy for the prevention of colorectal cancer.

Study shows colonoscopy better than sigmoidoscopy in protecting against colorectal cancer

September 18, 2013
A study in the Sept. 19 New England Journal of Medicine finds that colonoscopy appears to reduce the risk of developing or dying from colorectal cancer more powerfully than does sigmoidoscopy, a similar procedure that examines ...

Recommended for you

Retaining one normal BRCA gene in breast, ovarian cancers influences patient survival

August 22, 2017
Determining which cancer patients are likely to be resistant to initial treatment is a major research effort of oncologists and laboratory scientists. Now, ascertaining who might fall into that category may become a little ...

Study provides insight into link between two rare tumor syndromes

August 22, 2017
UCLA researchers have discovered that timing is everything when it comes to preventing a specific gene mutation in mice from developing rare and fast-growing cancerous tumors, which also affects young children. This mutation ...

Study identifies miR122 target sites in liver cancer and links a gene to patient survival

August 22, 2017
A new study of a molecule that regulates liver-cell metabolism and suppresses liver-cancer development shows that the molecule interacts with thousands of genes in liver cells, and that when levels of the molecule go down, ...

Zebrafish larvae could be used as 'avatars' to optimize personalized treatment of cancer

August 21, 2017
Portuguese scientists have for the first time shown that the larvae of a tiny fish could one day become the preferred model for predicting, in advance, the response of human malignant tumors to the various therapeutic drugs ...

Scientists discover vitamin C regulates stem cell function, curbs leukemia development

August 21, 2017
Not much is known about stem cell metabolism, but a new study from the Children's Medical Center Research Institute at UT Southwestern (CRI) has found that stem cells take up unusually high levels of vitamin C, which then ...

Searching for the 'signature' causes of BRCAness in breast cancer

August 21, 2017
Breast cancer cells with defects in the DNA damage repair-genes BRCA1 and BRCA2 have a mutational signature (a pattern of base swaps—e.g., Ts for Gs, Cs for As—throughout a genome) known in cancer genomics as "Signature ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.