Skip to content

    Colorectal Cancer Health Center

    Font Size
    A
    A
    A

    Study Shows Colonoscopy Misses 4% of Cancers

    Patients Can Help Improve Accuracy of Colon Test
    By
    WebMD Health News

    Aug. 30, 2004 -- Colonoscopy is currently considered the best way to screen for and detect colon cancer, which is the second leading cause of cancer-related deaths in the U.S. and Canada. And while the test flags the vast majority of colon cancers, it's not perfect.

    Four percent of cancers on the right-hand side of the colon are not detected by colonoscopy, according to a Canadian study published in the journal Gastroenterology. Researchers specifically looked at cancer on the right side of the colon because that is where it occurs most.

    It's probably not a technological flaw, say researcher Linda Rabeneck, MD, MPH, a senior researcher associated with the Cancer Quality Council of Ontario, Canada, and colleagues. More likely, the problem is less-experienced doctors, incomplete exams, and/or improper patient preparation.

    In colonoscopy, patients are sedated while doctors insert a flexible, lighted tube through the rectum allowing doctors to look at the entire colon for abnormalities. The tube is attached to a video monitor and equipment which allows a biopsy to be taken.

    Rabeneck and colleagues studied health records of more than 4,900 Canadians diagnosed with colon cancer between 1997 and 2001. All had had at least one colonoscopy within three years before their treatment.

    In 96% of the cases, colonoscopy detected their colon cancer. But in a few patients -- 4% -- the test missed the cancer.

    "It is important that we inform patients who are undergoing colonoscopy that if a cancer is present, there is a small chance that it will be missed," write the researchers.

    That's no reason to cancel your colonoscopy appointment. True, few patients look forward to the exam, but it does find almost all cancers, according to Rabeneck's study.

    In fact, colonoscopy's accuracy rate beats that of two other standard cancer screening tests: mammography for breast cancer and Pap smears for cervical cancer.

    If you're due for a colonoscopy, you may want to look for a practitioner with extensive experience and follow any pretest instructions to the letter. Know that no test is perfect, but remember that colonoscopy is still considered the best method for detecting colon cancer while it can be treated.

    Today on WebMD

    Colorectal cancer cells
    The right diagnosis is the most important factor.
    man with a doctor
    Our health check will steer you in the right direction.
     
    sauteed cherry tomatoes
    Fight cancer one plate at a time.
    bladder cancer x-ray
    Do you know the warning signs?
     
    bread
    ARTICLE
    Colon vs Rectal Cancer
    VIDEO
     
    New Colorectal Treatments
    VIDEO
    can lack of sleep affect your immune system
    FEATURE
     
    Cancer Facts Quiz
    QUIZ
    Virtual Colonoscopy
    VIDEO
     
    Picture of the Colon
    ANATOMY
    Vitamin D
    SLIDESHOW