Colorectal Cancer Screening by alicejenny


									                                               Colorectal Cancer Screening 2009
          Clinical Scenarios with Questions
          Answers and Discussion (FAQs)
          USPSTF most recent update

Clinical Scenarios
     1. Stan is a 53 yo WM without significant PMHx who presents to your office for a routine check
        because his “wife made me.” He has no complaints so you quickly turn the discussion toward
        health maintenance issues. A relatively savvy medical consumer – and slight skeptic, Stan has
        several questions for you regarding colorectal cancer and screening:

               a. What’s my risk?
               b. What puts me at risk?
               c. Is there anything that I can do to lower my risk? …I heard something about aspirin on
                  the news the other day.

     2. After hearing your explanations, Stan decides that he’s willing to consider screening options.
        But of course, he has more questions:

               a.    What options are there for screening?
               b.    Is there any proof they work?
               c.    What’s it gonna cost me?
               d.    If it’s normal, how long before you’re gonna wanna do it again?
               e.    What if it’s positive?

     3. Lisa is a 42 yo BF you’ve seen for 5 years with well-controlled HTN. As you entered the room,
        you overheard your nurse consoling her on the death of her brother. You learn that he died
        from colon cancer and was only 46.

               a. When should you start screening people?
                      i. Average risk?
                     ii. Family history of colorectal cancer?
                    iii. Inflammatory bowel disease?
                    iv. Polyposis syndromes?
               b. When can you stop screening?

     4. Alan is a 66 yo who returns to your office for follow-up of a recent polypectomy that was
        performed after you had encouraged him to have a screening colonoscopy. He says the test
        caused him to pass gas “like an Evinrude,” but he is glad that he did it. When should he be

          1   J. R. Hartig
              Last updated: February 10th, 2009
                                                    Colorectal Cancer Screening 2009

Answers and Discussion
1a.       Colorectal Cancer Risk

Colorectal Cancer (CRC) is relatively common. The lifetime risk for CRC is approximately 5%. 1 in 3
diagnosed with CRC will die from their disease – with the average person losing 13 years of expected
life. The majority of cases occur after age 50. CRC accounts for 10% of all cancer-related death.

More than 80% of colorectal cancers arise from adenomatous polyps. Although less than 1% of
adenomatous polyps less than 1 cm will eventually develop into cancer, 10% of adenomatous polyps
greater than 1 cm become malignant within 10 years, and about 25% become malignant after 20 years.
The prevalence of adenomatous polyps increases from 20% to 25% at age 50 to 50% by age 75-80.

A few more numbers to consider:
        Annual new diagnosis:                    ~145,000
        Annual deaths in the U.S.:               ~55,000
        Five-year survival (all type/stage):     61%
        Risk:     Average:                       5%
                  Family History:                           1.7 times increase risk (a single 1 degree relative)
                  Personal History polyp:                   3-7 times increase risk (polyp type matters)
                  IBD:                                      5-15 times increased
                  Polyposis syndromes:                      varies with type but ~ 90% by age 45

1b.      Risk Factors
         Age:                                      Rare before the age of 40. Greater than 90% of cases occur after the age
                                                   50. (Coincides with distribution of polyps in these ages.)

         Polyps:                                   Majority (80%) of CRC arise from adenomatous polyps. At age 50 the
                                                   prevalence of polyps is 25%. At age 75 it is 50%.

         FHx of CRC or adenomatous polyps:         These two appear to carry the same weighted risk.

         Geography :                               Whatever the cause, the rates of CRC are highest in North America,
         (genetic vs environmental vs other)       Australia, and northern and western Europe.

         IBD:                                      The risk begins to rise 10 years after diagnosis of pancolitis. Clearly
                                                   associated with UC, but Crohn’s appears to have similar risk as well.

         DM and insulin resistance:                Nurses Health Study ~1.5 times risk. Thought possibly that higher insulin
                                                   levels acting as a growth hormone increase risk.

         Cholecystectomy:                          associated with increased risk of right-sided colon cancers

         Alcohol:                                  modest increase risk noted. Greater amount of alcohol = greater risk

         Cigarette smoking:                        clearly demonstrated long-term smoking increases risk

         Ureterocolic anastomoses:                 Increase risk adjacent to the anastomsis.

         Previous pelvic/prostate irradiation:     possibly increases risk

         Red or processed meat consumption:        long-term consumption was associated with increased risk in a large

        2    J. R. Hartig
             Last updated: February 10th, 2009
                                                     Colorectal Cancer Screening 2009
                                                     epidemiology study
1c.      Risk Factor Modification (beyond cessation and control of above where possible)

         Diet:                 Diets high in fruit and vegetables have been shown to reduce the risk by as much as half among
                               groups in some studies. However, there are other studies that fail to confirm these findings

         Fiber:                conflicting results

         Folic Acid:           may reduce the risk of CRC, but benefit not seen until ~15 years and controversy remains
                               regarding the formulation (diet vs supplement) needed.

         Calcium:              Several studies have demonstrated a protective effect of calcium. It is most effective at
                               preventing distal carcinomas. Dose needed is somewhat unclear, but is recommended as both a
                               primary and secondary preventive measure by AGA.

         Magnesium:            reduces risk (animal studies and data from Swedish population study)

         Physical Activity:    associated with lower risk of CRC

         ASA and NSAIDs:       Substantial evidence suggests aspirin and perhaps NSAIDS reduce the long-term risk of CRC.
                               However, what role aspirin should have as a primary or secondary preventative measure is
                               unclear (dose that provided effect was relatively high thus making risk-benefit unclear)

         HRT:                  Women’s Health Study demonstrated reduction – others did not.

         Statins:              data conflicting but some evidence to suggest these lower risks.

         BOTTOM LINE: Quit smoking and drinking, eat right, exercise more and consider some of the
         above just like your mother told you… (calcium as part of osteoporosis regiment, etc.)

2acd.    Options for CRC screening – Summary of tests with some pros/cons

Test                    Pros                                         Cons                                   Interval

Home FOBT               Cheap, low risk (itself)                     False+ in screening programs           q1y
Flexible                No sedation, less prep                       Examines only half colon;              q5y
sigmoidoscopy                                                        1-2:10,000 perforation, $$
Flex sig and FOBT       Improved detection                           Not clear if continued FOBT adds       q5y (?)
                                                                     anything, $$
DCBE                    Whole colon, less risk than scope, misses    Similar prep to colonoscopy, no tissue q5-10y
                        distal colon lesions because of catheter     Dx or Tx,
                                                                     1:25,000 perforation, $$
Colonoscopy             Screen, Dx, Tx. Gold standard                $$$, 2:1000 perforation,               q10y
                        Sensativity/Specificity                      prep is not well tolerated, sedation
                                                                     required (risk)
CT Colography           15min, less invasive                         Same prep as colon, $$$,               ?
                                                                     no data to support use yet,
                                                                     radiation involved

                       Recommended by the USPSTF in 2008 paper

        3     J. R. Hartig
              Last updated: February 10th, 2009
                                                 Colorectal Cancer Screening 2009
A few notes:

FOBT should be used on three consecutive stool samples obtained at home by the patient and returned
to the physician. Rehydration of samples increases sensitivity but also increases the false positive rates.
Sensitivity and specificity of a single test have been estimated at 40% and 96% to 98%, respectively.
Hydration of specimen increases sensitivity (60%) but reduces specificity (90%).

In 3 recent randomized trials, performing flexible sigmoidoscopy in addition to FOBT yielded
approximately 7 additional cancers or large polyps per 1,000 patients compared to FOBT alone. Adding
FOBT did not improve the yield over sigmoidoscopy alone at the initial screening in these studies, which
used flexible sigmoidoscopy, but did in an earlier study that used rigid sigmoidoscopy.

Previous studies have reported high sensitivity (86% to 90%) of DCBE for colorectal cancer and polyps,
and high specificity (95%). In the National Polyp Study, however, DCBE detected only 48% of polyps
greater than 1 cm. Sensitivity might be higher in a typical screening population where the proportion of
large polyps is higher. Specificity of DCBE in this study was 85%.

Neither DRE nor single office occult testing is recommended in colorectal cancer screening.

2bd.     Data supporting each method with outcome of mortality

Test                                Mortality Decreased
Home FOBT                           RCTs
Flexible sigmoidoscopy              Case control studies
                                    On-going RCTs
Flex sig and FOBT                   No data for combined
Colonoscopy                         No data
DCBE                                No data
CT Colography                       No data

Despite lack of date demonstrating decreased mortality, most experts would agree that colonoscopy
should cut mortality.

2e.      Follow-up for any positive test should be a colonoscopy with biopsy and removal of lesions.

3a.      i.         50yo (consensus – some data to suggest little benefit to screen earlier…)
         ii.        As a rule… 10 years before first relative diagnosed or beginning at age 40 whichever
                    comes first. Repeat screening every 5 years.
         iii.       There is not specific evidence to answer this question. However: “It is common practice
                    to perform surveillance colonoscopy every one to two years beginning after eight years
                    of disease in patients with pancolitis, or after 15 years in those with colitis involving only
                    the left colon.” - UpToDate
         iv.        FAP – strongly consider colectomy. Flex sig yearly beginning at puberty
                    HNPCC – examination of the entire colon every 1-2 years beginning age 20-30 and yearly
                    after te age of 40. Consider genetic testing/counseling for both.

        4       J. R. Hartig
                Last updated: February 10th, 2009
                                           Colorectal Cancer Screening 2009
3b.     There are few data to determine optimal age for starting or stopping screening. FOBT has been
proven effective for persons aged 50-80 and sigmoidoscopy is associated with reduced mortality in
persons older than 45. One cost-effectiveness model suggests that beginning screening at age 40 rather
than at age 50 would offer less than a 1-day average improvement in life expectancy. Randomized trials
suggest that a life expectancy of at least 5 years may be required to realize the benefits of screening.
        The USPSTF recommends routinely screening individuals age 50-75. They recommend against
routine screening for individuals age 76-85 though they acknowledge that individual patient factors
must be considered. The recommend against screening in individuals >85 years. The new
recommendations regarding ages to stop screening are based upon the risk:benefit ratio related to the

4.       Answer depends on many factors, but for most adenomatous polyps, a repeat colonscopy
should be performed 3 years after removal of original polyp. (Large initial lesions may require a much
closer follow-up to be determined by the endoscopist.)

Link to the latest UPSPTF Update:

      5    J. R. Hartig
           Last updated: February 10th, 2009

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