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- Malignant neoplasm involving colon, rectum, and anal canal
- Studies suggest development of colorectal cancer related
- Dietary factors
- Lifestyle factors
- Physical and genetic susceptibilities
- Multistep process of genetic and phenotypic alterations
of normal bowel epithelium structure and function leading to unregulated
cell growth, proliferation, and tumor development.
- Features of colorectal tumorigenesis include:
- Activation of oncogene pathways
- Mutational inactivation of tumor-suppressor genes
- Activation of growth factor pathways
- Adenocarcinomas account for >90% of tumors of large
- Third leading cause of cancer-related deaths for men and
women in United States.
- Median age at diagnosis is 70 years.
- Primary prevention aimed at populations at highest risk.
- Secondary prevention aimed at preventing malignancy in population
already manifesting initial disease process.
procedures ranging from colonoscopic removal of precancerous polyps
detected during screening colonoscopy to total colectomy for high-risk
individuals (e.g., familial adenomatous polyposis [FAP]).
- Screening techniques
- Fecal occult blood testing
- Flexible sigmoidoscopy: not able to evaluate entire bowel
- Total colonic examination
- Double-contrast barium enema
- United States screening guidelines for average-risk
individuals include annual occult fecal blood testing starting at
age 50 years and examination of colon every 5 or 10 years, depending
- Elevated risk
- Physical inactivity and
- Alcohol intake: stronger association for men than women
- Tobacco use
- Western diet
- Clinical risk factors
- Type 2 diabetes, independent
of BMI and physical activity
- Chronic inflammatory diseases
- Ulcerative colitis
- Crohn’s disease
- Genetic susceptibility
- Hereditary (10% of
- Hereditary nonpolyposis colorectal cancer (HNPCC)
- Familial (20% of cases)
relatives have 2–4 times increased risk as compared to
- Reduced risk
- Risk-to-benefit considerations
- Regular aspirin and NSAID use associated
with risk reduction of 30–50%.
- Exogenous postmenopausal oral hormone replacement therapy
reduces risk by about 20%.
- Vitamin D and calcium appear to interact synergistically
to protect against adenoma recurrence and colorectal cancer.
- Signs and symptoms can be extremely varied,
subtle, and nonspecific.
- Patients with early-stage colorectal cancer often asymptomatic,
and lesions usually detected by screening procedures.
- Approximately 19% of patients present with metastatic
- Most common site of metastasis is liver,
followed by lungs and bones.
- Blood in stool most common sign.
- Any change in bowel habits
- Vague abdominal discomfort
- Abdominal distension
- Fatigue (if anemia is severe)
Means of Confirmation
- Pathologic examination of surgical specimens
- Complete blood count (CBC): iron deficiency anemia from
- Guaiac stool test: positive if blood in stool
- Carcinoembryonic antigen (CEA): elevated in most patients
- Metabolic panel: Liver function test (LFT) elevated with metastatic