Background

Question 1

What is the incidence of rectal cancer in the United States?

Answer 1

34,000 cases/yr of rectal cancer in the United States.

Question 2

What is the median age for rectal cancer?

Answer 2

The median age for rectal cancer is the 7th decade of life.

Question 3

What is the incidence of colon cancer in the United States?

Answer 3

The incidence of colon cancer in the United States is 180,000 cases/yr and is the #2 cause of cancer deaths in the United States after lung cancer.

Question 4

What is the median age for sporadic colon cancer?

Answer 4

The median age for sporadic colon cancer is 63 yrs.

Question 5

What is the sup/cranial extent of the rectum, and how long is it?

Answer 5

The rectum begins at S3 and is ~15 cm long.

Question 6

Show Answer

What are the most common sites of mets in rectal cancer?

Answer 6

Rectal cancer metastasizes mostly to the liver (via the sup rectal vein) and next the lung (via the mid and inf rectal veins).

Question 7

Where in the GI tract does small bowel cancer most frequently arise?

Answer 7

Small bowel cancer arises most frequently in the duodenum (duodenum > jejunum > ileum).

Question 8

What type of adenomas are more likely to progress to invasive rectal cancer?

Answer 8

Villous adenomas are more likely to progress to invasive rectal cancer (than tubular adenomas).

Question 9

How are avg-risk individuals defined as far as colorectal cancer is concerned?

Answer 9

Avg-risk colorectal individuals are ≥50 yo asymptomatic pts without a family Hx of colorectal cancer.

Question 10

What are the colorectal cancer screening options for avg-risk individuals?

Answer 10

Colonoscopy (q10yrs), fecal occult blood test (q1yr), and sigmoidoscopy (q5yrs) or double-contrast barium enema (q5yrs) are the colorectal screening options for avg-risk individuals.

Question 11

How frequently should individuals with inflammatory bowel disease (IBD) have a screening colonoscopy?

Answer 11

Individuals with IBD should undergo a screening colonoscopy q1–2yrs.

Question 12

How frequently should individuals with a family Hx of colorectal cancer have a screening colonoscopy? When should screening begin for such individuals?

Answer 12

Individuals with a family Hx of colorectal cancer should have a colonoscopy q1–5yrs and should begin at age 40 yrs or 10 yrs prior to the earliest cancer Dx in the family.

Question 13

What are the dietary risk factors for developing colorectal cancer?

Answer 13

Risk factors for colorectal cancer include a diet rich in fat and low in fiber and antioxidants.

Question 14

Is smoking a risk factor for colorectal cancer?

Answer 14

Yes. Smoking is a risk factor for colorectal cancer. (Stürmer T et al., JNCI 2000)

Question 15

Which supplements and which drug have shown promise as chemopreventative agents in colorectal cancer?

Answer 15

Calcium, vitamin D, and folic acid supplementation have shown some benefit in preventing colorectal cancer, while aspirin administration has been associated with a lower risk of developing colorectal polyps.

Question 16

What are 2 common familial/heritable risk factors for colorectal cancer?

Answer 16

The 2 most common familial conditions associated with colorectal cancer are FAP and HNPCC (aka Lynch syndrome).

Question 17

What % of colorectal cancer cases are attributable to HNPCC?

Answer 17

5% of colorectal cancer cases are attributable to HNPCC.

Question 18

What 2 familial syndromes, other than FAP and HNPCC, have been associated with a higher risk for developing colon cancer?

Answer 18

Cowden syndrome and Gardner syndrome predispose pts to developing colon cancer (in addition to other cancers).

Question 19

Initial mutation of what tumor suppressor gene leads to a greater chance for developing colorectal cancer? With what familial condition is this mutation associated?

Answer 19

Initial mutation in the APC tumor suppressor gene leads to a higher chance for developing colorectal cancer; this mutation is also associated with FAP.

Question 20

Mutation of what oncogene leads to a greater chance for developing colorectal cancer?

Answer 20

Initial mutation in the K-ras oncogene leads to a higher chance for developing colorectal cancer.

Question 21

Most familial HNPCC cases have been associated with mutations in what genes? What do these genes regulate?

Answer 21

Most familial cases identified as HNPCC have been associated with mutations in the hMLH1 or hMSH2 gene, which regulate mismatch repair.

Question 22

Pts with what chronic inflammatory condition are at a >20-fold increased risk for developing colorectal cancer?

Answer 22

Pts with ulcerative colitis are at a >20-fold increased risk for developing colorectal cancer.