Colorectal and Small Bowel Cancer

Colorectal and Small Bowel Cancer Colorectal and Small Bowel Cancer

Boris Hristov and Joseph M. Herman

Background

What is the incidence of rectal cancer in the U.S.?

34,000 cases/yr of rectal cancer in the U.S.

What is the median age for rectal cancer?

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

What is the incidence of colon cancer in the U.S.?

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

What is the median age for sporadic colon cancer?

The median age for sporadic colon cancer is 63 yrs.

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

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

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

Rectal cancer metastasizes mostly to the liver (via the sup rectal vein) → and the lung.

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

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

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

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

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

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

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

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.

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

Individuals with IBD should undergo a screening colonoscopy every 1–2 yrs.

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

Individuals with a family Hx of colorectal cancer should have a colonoscopy every 1–5 yrs and should begin screening at age 40 yrs or 10 yrs prior to the earliest cancer Dx in the family.

What are the dietary risk factors for developing colorectal cancer?

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

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

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

What % of colorectal cancer cases are attributable to HNPCC?

5% of colorectal cancer cases are attributable to HNPCC.

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

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

Is smoking a risk factor for colorectal cancer?

Yes. Smoking is a risk factor for colorectal cancer. (St¨rmer T et al., J Natl Cancer Inst 2000)

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

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.

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

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

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

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

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

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

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

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

Workup/Staging

What is the most common presenting Sx in rectal cancer?

Hematochezia is the most common presenting Sx in rectal cancer.

What must the physical exam include for pts with suspected rectal cancer?

The physical must include DRE (pelvic exam for women) for presumed rectal cancer pts.

How is the Dx of rectal cancer typically established?

Endoscopic Bx is a typical way of establishing the Dx. A full colonoscopy should be performed to r/o more proximal lesions.

What studies are performed in the workup of rectal cancer pts, and what is the purpose of each modality?

For staging purposes, EUS must be performed in rectal cancer pts. To r/o metastatic Dz, CT C/A/P is performed.

What labs are collected as part of the staging workup for colorectal cancers?

Labs for the workup of colorectal cancer: CBC, Chem 7, LFTs, CEA

Is a PET scan routinely indicated for pts with rectal cancer?

No. A PET scan is not routinely indicated in pts with localized rectal cancer.

What is the AJCC 7^th edition (2009) T staging for colorectal cancer?

The T staging for rectal cancer is based on the DOI:

Tis: CIS or invasion into lamina propria
T1: invades submucosa
T2: invades muscularis propria
T3: invades through muscularis and into pericolorectal tissues
T4a: penetrates surface of visceral peritoneum
T4b: invades or adheres to adjacent organs

What is the AJCC 7^th edition (2009) N staging for colorectal cancer?

In the 2002 edition of AJCC, N1 designated involvement of 1–3 regional LNs, whereas N2 designated involvement of ≥ 4 LNs.

In the AJCC 7^th edition, N1 and N2 are further broken down:

N1a: mets to 1 regional LN
N1b: mets to 2–3 regional LNs
N1c: tumor deposits in subserosa, mesentery, or nonperitonealized pericolic or perirectal tissues without regional LN mets
N2a: mets to 4–6 LNs
N2b: mets to ≥7 LNs

What is the AJCC 7^th edition (2009) breakdown of M staging for colorectal cancer?

M1a: DMs to a single organ or site (e.g., liver, lung, ovary, nonregional LNs)
M1b: mets >1 organ/site or deposits in peritoneum

What are the AJCC 7^th edition (2009) TNM stage groupings for colorectal cancer?

Stage I: T1-2N0
Stage IIA: T3N0
Stage IIB: T4aN0
Stage IIC: T4bN0
Stage IIIA: T1-2N1 or N1c; T1N2a
Stage IIIB: T3-4aN1 or N1c; T2-3N2a; T1-2N2b
Stage IIIC: T4aN2a; T3-4aN2b; T4bN1-2
Stage IVA: TXNXM1a
Stage IVB: TXNXM1b

How does the old Dukes staging for colorectal cancers correspond to the current AJCC staging system?

Dukes A: stage I
Dukes B: stage II
Dukes C: any nodal involvement (or stage III)

What is the AJCC 7th edition (2009) T staging for small intestine cancers?

Tis: CIS
T1a: lamina propria
T1b: submucosa
T2: muscularis propria
T3: through muscularis propria into subserosa or into mesentery/retroperitoneum ≤2 cm.
T4^*: perforates visceral peritoneum or invades adjacent organs (including other loops of small bowel, mesentery or retroperitoneum >2 cm, and abdominal wall (extension from serosa)