02-28 CRC Screening

Question 1

<p>OBJECTIVE: Discuss the epidemiology of colorectal cancer</p>

Answer 1

<p>From notes:</p>

<ul>
<li>i. 3rd most common cause of cancer in men and women</li>
<li>ii. 2nd most common cause of cancer death in the United States</li>
<li>iii. In US Roughly 140,000 incident cases each year/approximately 50,000 deaths each year</li>
<li>iv. Recent trends in incidence and mortality (over last 20+ years) encouraging</li>
</ul>

Question 2

<p>OBJECTIVE: Describe the basic pathophysiology of colorectal cancer including the adenoma-carcinoma sequence</p>

Answer 2

<ul>
<li>i. Traditional Polyp-Cancer Sequence
<ul>
<li>Normal epithelium</li>
<li>tubular adenoma</li>
<li>tubulovilous adenoma</li>
<li>vilous adenoma</li>
<li>adenocarcinoma</li>
</ul>
</li>
<li>ii. Most (?70%) sporadic cancers derive from an initial sporadic mutation in <strong>APC gene</strong></li>
<li>iii. Accumulation of genetic mutations over time with growth to invasive cancer</li>
</ul>

Question 3

<p>OBJECTIVE: Discuss the current CRC screening options available, compare and contrast their strengths and weaknesses</p>

Answer 3

<p><em>The USPSTF give all<strong>&nbsp;</strong>3 options<strong>&nbsp;A-level evidence</strong> for CRC prevention in adults <strong>50-75 y/o</strong>.</em></p>

<p>FOBT</p>

<ul>
<li>Can do at home</li>
<li>qYear</li>
<li>Two methods:
<ol>
<li>Conventional FOBT (test for globin rxn)</li>
<li>FIT (Ab/Ag testing for hgb)</li>
</ol>
</li>
<li>Drawbacks: many false positives, have to touch your poo</li>
</ul>

<p>Flexible Sigmoidoscopy</p>

<ul>
<li>examine left colon (i.e. to splenic flexure)</li>
<li>q5 yrs if last one normal</li>
<li>less bowel prep and sedation needed</li>
<li>drawback: if you find anything have to do colo</li>
<li><em>Can be done by Family Med docs!</em></li>
</ul>

<p>Colonoscopy</p>

<ul>
<li>entire colon to cecum</li>
<li>only need to repeat q10 yrs if negative</li>
<li>drawback: more extensive bowel prep, sedation, messes up pt&#39;s day; more expensive</li>
</ul>

Question 4

<p>OBJECTIVE: Describe the characteristics of an ideal &quot;screenable&quot; disease</p>

Answer 4

<ol>
<li>common disease</li>
<li>associated w/ high morbidity/mortality</li>
<li>has an identifiable and <u>treatable</u> pre-clinical phase</li>
</ol>

Question 5

<p>OBJECTIVE: Discuss and evaluate the strength of the evidence supporting the current recommendations for CRC screening</p>

Answer 5

<p>Both FOBT and sigmoidoscopy have <u>RCT data</u>&nbsp;showing&nbsp;&darr; in CRC mortality</p>

<ul>
<li>15-30% for FOBT</li>
<li>22-31% for Sigmoidoscopy</li>
</ul>

<p>Colonoscopy has better stats (~50% &darr;)&nbsp;<strong>but</strong> these are based on <u>observational data</u>&nbsp;only.</p>

<ul>
<li>While colonoscopy goes all the way to the cecum, there is little statistically significant evidence that it reduces mortality from cancers that are beyond the view of the sigmoidoscope.</li>
</ul>

Question 6

<p>OBJECTIVE: Use CRC screening as a vehicle to describe how we determine and/or measure (at the systems level) the effectiveness of screening programs</p>

Answer 6

<p>Key points I took</p>

<ul>
<li>hierarchy of study designs (RCT is gold std; see image here)</li>
<li>importance of picking outcomes to follow</li>
<li>you can do studies using SEER data which gives average U.S. incidence for a particular cancer and see if your intervention decreased incidence relative to those data</li>
<li>probably other things...</li>
</ul>