Colon Cancer

Introduction

Colon cancer or colorectal cancer is cancer of the large intestine (colon), which is the lower part of the digestive system. Rectal cancer is cancer of the last several inches of the colon and this is also included in colorectal cancer.

Most colon cancers begin as small, noncancerous (benign) clumps of cells called as adenomatous polyps. Over time some of these polyps can become colon cancers.

Other rare types of cancer can affect the colon, such as lymphoma, carcinoid tumors, melanoma, and sarcomas. However, colonic carcinoma is the most important cancer of colon.

Causes:

Colorectal cancer is one of the leading causes of cancer-related deaths in the world. However, early diagnosis can often lead to a complete cure.

Higher risk of colon cancer is expected in case of the following:

1. Age more than 60 years

2. Diet high in red or processed meats

3. Cancer elsewhere in the body

4. Presence of colorectal polyps

5. Patients with inflammatory bowel disease (Crohn’s disease or ulcerative colitis)

6. Family history of colon cancer

7. Personal history of breast cancer

8. Certain genetic syndromes also increase the risk of developing colon cancer. Two of the most common are:

• Familial adenomatous polyposis (FAP)

• Hereditary nonpolyposis colorectal cancer (HNPCC), also known as Lynch syndrome

1. Eating high-fat and low-fiber diet.

2. Smoking cigarettes and drinking alcohol.

Causes

Many cases of colon cancer have no symptoms. The following symptoms, however, may indicate colon cancer:

1. Abdominal pain and tenderness in the lower abdomen

2. Blood in the stool

3. Diarrhea, constipation, or other change in bowel habits

4. Weight loss without any known reason

Exams and Tests:

In case if the doctor diagnoses colorectal cancer, more tests will be done to see if the cancer has spread.

Complete medical history and physical examination of abdomen is performed. The physical exam rarely shows any problems, although in some cases a lump (mass) in the abdomen may be felt. A rectal exam may reveal a mass in patients with rectal cancer, but not colon cancer.

A fecal occult blood test – this test may detect small amounts of blood in the stool, which could suggest colon cancer.

Colonoscopy- this is the best imaging study and also the screening test for colon cancer as it can visualize the entire colon.

Sigmoidoscopy

Blood tests such as Complete blood count (CBC) to check for anemia and liver function tests

Staging of cancer

In case if the doctor diagnoses colorectal cancer, more tests will be done to see if the cancer has spread. This is called staging. CT or MRI scans of the abdomen, pelvic area, chest, or brain may be used to stage the cancer. Sometimes, PET scans are also used.

Stages of colon cancer are:

Stage 0: Very early cancer on the innermost layer of the intestine

Stage I: Cancer is in the inner layers of the colon

Stage II: Cancer has spread through the muscle wall of the colon

Stage III: Cancer has spread to the lymph nodes

Stage IV: Cancer has spread to other organs

Blood tests to detect tumor markers, including carcinoembryonic antigen (CEA) and CA 19-9, may help the physician to evaluate the treatment.

Treatment

In general, treatments for colon cancer may include:

Surgery (most often a colectomy) to remove cancer cells – Stage 0 colon cancer may be treated by removing the cancer cells, often during a colonoscopy. For stages I, II, and III cancer, more extensive surgery is needed to remove the cancerous part of the colon.

Chemotherapy- this is done to kill cancer cells

Almost all patients with stage III colon cancer should receive chemotherapy after surgery for approximately 6 – 8 months. This is called adjuvant chemotherapy. In stage IV colon cancer, chemotherapy can reduce symptoms and improve survival. Irinotecan, oxaliplatin, capecitabine, and 5-fluorouracil are the three most commonly used drugs.

Monoclonal antibodies, including cetuximab, panitumumab, bevacizumab, and other drugs have been used alone or in combination with chemotherapy.

RADIATION

Although radiation therapy is occasionally used in patients with colon cancer, it is usually used in combination with chemotherapy for patients with stage III rectal cancer.

For patients with stage IV disease that has spread to the liver, the treatments are directed specifically at the liver. This may include:

1. Burning the cancer (ablation)

2. Chemotherapy or radiation directly

3. Freezing the cancer (cryotherapy)3. Freezing the cancer (cryotherapy)

4. Surgery

Prognosis

In general, when treated at an early stage, many patients survive at least 5 years after their diagnosis. (This is called the 5-year survival rate.)

Possible Complications:

1. Blockage of the colon

2. Cancer recurrence

3. Cancer spreading to other organs or tissues (metastasis)

4. Development of a second primary colorectal cancer