Chapter 47: Colon and Rectum- Colorectal Ca Flashcards
What is it?
Adenocarcinoma of the colon or rectum
What is the incidence?
- Most common GI cancer
- Second most common cancer in the United States
- Incidence increases with age starting at 40 and peaks at 70 to 80 years
How common is it as a cause of cancer deaths?
Second most common cause of cancer deaths
What is the lifetime risk of colorectal cancer?
6%
What is the male-to-female ratio?
≈1:1
What are the risk factors?
Dietary: increased rates correlated with
- Low-fiber
- high-fat diets
Genetic: Family history is important when taking history
- FAP
- Lynch’s syndrome
IBD: Ulcerative colitis > Crohn’s disease
Age
previous colon cancer
What is Lynch’s syndrome?
HNPCC = Hereditary NonPolyposis Colon Cancer
- autosomal-dominant inheritance of high risk for development of colon cancer
What are current ACS recommendations for polyp/colorectal screening in asymptomatic patients without family (first-degree) history of colorectal cancer?
Starting at age 50, at least one of the following test regimens is recommended:
- Colonoscopy q10 yrs
- Double contrast barium enema (DCBE) q5 yrs
- Flex sigmoidoscopy q5 yrs
- CT colonography q5 yrs
What are the current recommendations for colorectal cancer screening if there is a history of colorectal cancer in a first-degree relative <60 years old?
Colonoscopy at age 40, or 10 years before the age at diagnosis of the youngest first-degree relative, and every 5 years thereafter
What signs/symptoms are associated with the following conditions:
Right-sided lesions?
Right side of bowel has a large luminal diameter, so a tumor may attain a large size before causing problems:
- Microcytic anemia
- occult/melena more than hematochezia PR
- postprandial discomfort
- fatigue
What signs/symptoms are associated with the following conditions:
Left-sided lesions?
Left side of bowel has smaller lumen and semisolid contents:
- Change in bowel habits (small-caliber stools)
- colicky pain
- signs of obstruction
- abdominal mass
- heme(+) or gross red blood
- Nausea, vomiting
- constipation
What is the incidence of rectal cancer?
Comprises 20% to 30% of all colorectal cancer
What are the signs/symptoms of rectal cancer?
Most common symptom is hematochezia (passage of red blood ± stool) or mucus; also:
- tenesmus
- feeling of incomplete evacuation of stool (because of the mass),
- rectal mass
What is the differential diagnosis of a colon tumor/mass?
- Adenocarcinoma
- carcinoid tumor
- lipoma
- liposarcoma
- leiomyoma
- leiomyosarcoma
- lymphoma
- diverticular disease
- ulcerative colitis
- Crohn’s disease
- polyps
Which diagnostic tests are helpful?
- History and physical exam (Note: ≈10% of cancers are palpable on rectal exam)
- heme occult
- CBC
- barium enema
- colonoscopy
What disease does microcytic anemia signify until proven otherwise in a man or postmenopausal woman?
Colon cancer
What tests help find metastases?
- CXR
- lung metastases
- LFTs
- liver metastases
- abdominal CT scan
- liver metastases
- other tests based on history and physical exam:
- head CT scan for left arm weakness looking for brain metastasis
What is the preoperative workup for colorectal cancer?
- History
- physical exam
- LFTs
- CEA
- CBC
- Chem 10
- PT/PTT
- type and cross 2 units PRBCs
- CXR
- U/A
- abdominopelvic CT scan
By what means does the cancer spread?
-
Direct extension:
- circumferentially and then through bowel wall to later invade other abdominoperineal organs.
-
Hematogenous:
- portal circulation to liver lumbar
- vertebral veins to lungs
- Lymphogenous: regional lymph nodes (LNs)
- Transperitoneal
- Intraluminal
Is CEA useful?
Not for initial screening but for baseline and recurrence surveillance (but offers no proven survival benefit)
What unique diagnostic test is helpful in patients with rectal cancer?
Endorectal ultrasound
- probe is placed transanally and depth of invasion andnodes are evaluated
How are tumors staged?
TMN staging system
Stage I
Invades submucosa or muscularis propria
T1–2
N0
M0
Stage II
Invades through muscularis propria or surrounding structures but with negative nodes
T3–4
N0
M0
