Although rare in developing countries, cancers of the colon and rectum are the second most frequent malignancy in Western countries.1 In the United States, colorectal cancer (CRC) is the third most common cancer diagnosed among men and women, and the second leading cause of death from cancer.2 The lifetime risk of developing colorectal cancer is estimated at 5–6%.3 More than 940,000 cases of colorectal cancer occur annually worldwide and nearly 500,000 die from it each year.1 The survival in colorectal cancer is related to the clinical and pathological stage of the disease at the time of diagnosis. Reductions in colorectal cancer morbidity and mortality can be achieved through detection and treatment of early-stage cancers, and the identification and removal of its precursors. Colorectal cancer screening tests have been shown to achieve this purpose.
The optimal approach to the treatment depends on a number of factors. Surgery is the primary treatment for stage I colorectal cancer. Adjuvant chemotherapy is recommended after resection in selected patients with stage II and in all patients with stage III disease. Significant improvements in survival have been demonstrated through combination of chemotherapy and monoclonal antibody regimens.4
Development of colorectal cancer ( Pathogenesis)
Colorectal cancer originates from the epithelial cells lining the GI tract. Almost all colorectal cancers arise from adenomatous polyps (APs). The development of APs by the age of 70 years is quite common, but only one tenth of these will proceed to cancer. It has been suggested that about 25% of colon cancer patients have certain degree of familial background and another 15% have a strong family history involving a first- or second-degree relative.5
It has been accepted that colorectal cancer is a progressive multistep genetic disease involving the inactivation of a variety of tumor-suppressor and DNA repair genes and simultaneous activation of certain oncogenes.6 In addition, epidemiologic studies have suggested that environmental factors support the development of colorectal cancer.
Symptoms of Colorectal CancerSymptoms of colorectal cancer
Risk Factors for Colorectal Cancer
Factors that increase a person’s risk of developing CRC include the following:
- Age—the risk increases with age.
- Presence of polyps of the colon, particularly APs.
- Personal history of colorectal cancer or adenomas at any age, or cancer of endometrium (uterus) or ovary diagnosed before age 50 years.
- Family history of colorectal cancer .
- Diet—a diet high in red meat and low in fresh fruit, vegetables and fish increases the risk of CRC.
- Long-standing IBD of the colon.
- Heavy alcohol consumption.
- Physical inactivity.
Cancer Screening and Diagnosis of Colorectal Cancer
As colorectal cancer (CRC) may take many years to develop and early cancer detection significantly improves the chances of cure, early screening is recommended in all individuals who are at increased risk. Screening programs should begin by classifying the patient’s level of risk based on personal, family and medical history, which will determine the appropriate approach to screening in that individual.
- Men and women at average risk should be offered colorectal cancer and APs screening as early as 50 years of age and repeated every 10 years.
- Individuals with a first-degree relative with colorectal cancer or APs diagnosed at the age of <60 years or 2 first-degree relatives diagnosed with colorectal cancer at any age should have screening colonoscopy at the of age 40 years or 10 years younger than the earliest diagnosis in their family, whichever comes first and repeated every 5 years.
- People with a first-degree relative with colorectal cancer or APs diagnosed at the age of ≥60 years or two second-degree relatives with colon cancer are screened as average risk persons, but beginning at the age of 40 years.
- People with 1 second-degree relative or third-degree relative with colorectal cancer should be screened as average risk people.
- Fecal occult blood test — yearly screening.
- Double contrast barium enema (DCBE) — every 5 years.
- Sigmoidoscopy — every 5 years.
- Colonoscopy — every 10 years.
- Computerized topographic (CT) colonography and magnetic resonance (MR) colonography.
- Fecal DNA testing.
Management of Colorectal Cancer
Treatment of colorectal cancer depends on the stage of the disease and the overall health of the patient. Staging of colorectal cancer is based on the extent of cancer invasiveness and dissemination. The preferred staging system is the TNM classification, developed by the American Joint Committee on Cancer (AJCC) and the International Union Against Cancer (UICC), which describes the primary tumor, regional lymph nodes and distant metastases.
Surgery is the treatment of choice for colorectal cancer. Chemotherapy and radiation therapy may be used as adjuvant. Surgery is indicated in nearly all patients with newly diagnosed cancer unless survival is unlikely or life expectancy is very short due to advanced cancer or other diseases.
The operative procedure consists of an en bloc resection of the involved bowel segment and regional lymphatic drainage. Primary anastomosis of a prepared bowel is possible in elective cases. In selected patients with moderately or well-differentiated cancers of the head of a polyp without any lymphatic, vascular or perineural invasion, an endoscopic polypectomy is preferred. Laparoscopic surgery has the advantage of a shorter hospital stay and a faster recovery time.
Chemotherapy is the primary mode of adjuvant therapy for patients with colorectal cancer.1 There is no much evidence for beneficial effects of adjuvant chemotherapy for patients with stage I an stage II colorectal cancer, but the beneficial effects of adjuvant chemotherapy for patients with stage III disease are well proven. The current standard duration of adjuvant treatment is 6 monthsand treatmentshould be initiated within 8 weeks postoperatively.1
Follow-up of Colorectal Cancer
Postoperatively, colonoscopy should be done annually for 5 years and every 3 years thereafter if no polyps or tumors are found. If preoperative colonoscopy was incomplete because of an obstructing cancer, a colonoscopy should be done 3 months after surgery.