Colorectal Cancer

Published on 04/03/2015 by admin

Filed under Hematology, Oncology and Palliative Medicine

Last modified 04/03/2015

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Chapter 77

Colorectal Cancer

Summary of Key Points

Epidemiology

• Colorectal cancer (CRC) is the second most common cancer in women and the third most common cancer in men worldwide.

• Within economically developed countries, the lifetime risk of developing CRC is 1 in 20.

• Because of increased screening rates, the incidence of CRC is declining for men and women in the United States.

• The incidence is 15 times higher in adults older than age 50 years, compared with those younger than age 50 years.

• Inherited genetic syndromes (hereditary nonpolyposis colorectal cancer [HNPCC] and familial adenomatous polyposis [FAP]: fewer than 10% of cases) and inflammatory bowel disease (IBD) in concert with dietary and environmental exposures increases risk for CRC.

• The 5-year overall survival rate has greatly improved in the last 2 decades, and is now approximately 65%, with variations across racial and ethnic subgroups.

• Mortality is 35% to 40% higher in men than in women.

Screening and Prevention of CRC

• High level of physical activity decreases the risk of CRC by up to 50%.

• Diets high in fiber and low in red, processed meat may alter risk of CRC.

• Calcium/vitamin D supplementation might have preventive effects.

• Aspirin and cyclooxygenase (COX)-2 inhibitors may prevent polyps and CRC, but are only recommended in high-risk patients.

• Premenopausal hormone replacement therapy reduces the incidence of CRC, but increases the risk of breast cancer and cardiovascular complications.

• There are mixed results in studies of the effects of statins on CRC risk.

• Colonoscopy is the mainstay of screening and a useful tool in the diagnosis of CRC. Sigmoidoscopy may reduce CRC incidence and mortality.

• Fecal occult blood is an acceptable screening tool.

• Virtual colonoscopy, the detection of abnormal DNA within stool sample and capsule endoscopy are potentially new screening tests.

• Screening is based on risk categories that take into account age; race; personal history of IBD, polyps, or cancer; family history of CRC; and presence of hereditary syndromes.

Diagnosis and Staging

• CRC is often insidious in development, underscoring the importance of screening.

• Altered bowel habits, blood per anum, fatigue, anemia, and weight loss are frequent symptoms.

• Obstruction is the most common acute surgical problem (approximately 30% of left-sided lesions present with an obstruction).

• Approximately 5% of CRC patients will be diagnosed with synchronous cancer. The liver is the most common site for synchronous metastasis.

• Approximately 20% to 40% will have synchronous polyps with cancer primary.

• Computed tomography (CT) scan, magnetic resonance imaging (MRI), and positron emission tomography (PET) are imaging tools used in the staging of CRC.

• Intraoperative ultrasound is the most sensitive method to evaluate liver for metastases.

• Tumor size is not as critical as depth of invasion and nodal status in determining prognosis.

• High histologic grade, lymphatic invasion, venous invasion, and involvement of surgical resection margins are independent adverse prognostic factors.