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
Stage III
Positive nodes, no distant metastasis
any T
N1–3
M0
Stage IV
Positive distant metastasis
any T
any N
M1
What is the approximate 5-year survival by stage:
Stage I?
90%
What is the approximate 5-year survival by stage:
Stage II?
70%
What is the approximate 5-year survival by stage:
Stage III?
50%
What is the approximate 5-year survival by stage:
Stage IV?
10%
What percentage of patients with colorectal cancer have liver metastases on diagnosis?
≈20%
What are the common preoperative IV antibiotics?
Cefoxitin (Mefoxin®)
carbapenem
If the patient is allergic (hives, swelling), what antibiotics should be prescribed?
IV Cipro® (ciprofloxacin) and Flagyl® (metronidazole)
What are the treatment options?
Resection: wide surgical resection of lesion and its regional lymphatic drainage
What decides low anterior resection (LAR) versus abdominal perineal resection (APR)?
Distance from the anal verge and pelvis size
What do all rectal cancer operations include?
Total mesorectal excision
- remove the rectal mesentery including the LNs
What is the minimal surgical margin for rectal cancer?
2 cm
How many LNs should be resected with a colon cancer mass?
12 LNs minimum = for staging, and may improve prognosis
What is the adjuvant treatment of stage III colon cancer?
5-FU and leucovorin (or levamisole) chemotherapy (if there is nodal metastasis postoperatively)
What is the adjuvant treatment for T3–T4 rectal cancer?
Preoperative radiation therapy and 5-FU chemotherapy as a “radiosensitizer”
What is the most common site of distant (hematogenous) metastasis from colorectal cancer?
Liver
What is the treatment of liver metastases from colorectal cancer?
Resect with ≥1 cm margins and administer chemotherapy if feasible
What is the surveillance regimen?
- Physical exam
- stool guaiac
- CBC
- CEA
- LFTs
- every 3 months for 3 years
- then every 6 months for 2 years)
- CXR
- every 6 months for 2 years
- and then yearly
- colonoscopy
- at years 1 and 3 postoperatively
- CT scans directed by exam
Why is follow-up so important the first 3 postoperative years?
≈90% of colorectal recurrences are within 3 years of surgery
What are the most common causes of colonic obstruction in the adult population?
- Colon cancer
- diverticular disease
- colonic volvulus
What is the 5-year survival rate after liver resection with clean margins for colon cancer liver metastasis?
≈33% (28% to 50%)
What is the 5-year survival rate after diagnosis of unresectable colon cancer liver metastasis?
0%
