The lowest part of the digestive system is called the colon. The last six inches of the colon are also called the rectum. After digestion of food, residues are discharged through the colon and rectum (commonly known as the large intestine). Cancer growing in this area is called colorectal cancer (or colon, rectal cancer).

Most colorectal cancers originally appear as small, non-cancerous, benign colorectal polyps. Colorectal polyps are protrusions that grow on the surface of intestinal mucosa. After a period of time, some colon polyps will deteriorate into colorectal cancer.

With the change of people's diet, living habits and environment, the incidence of colorectal cancer has been on the rise, about which people should be very careful.

Symptoms

Early detection of colorectal cancer is not easy, because when colorectal cancer first forms, it is only a small mass of cancer cells, which does not cause intestinal symptoms. Symptoms would only occur when it gradually grows larger.

When colorectal cancer occurs in the right-side large intestine (i.e. cecum and ascending colon), abdominal distension or occult blood reaction in stool will be positive, i.e. hematochezia. When it occurs in the left-side (i.e. descending colon, sigmoid colon, rectum), abdominal pain, blood in stool or changes in stool habits (e.g. diarrhea or constipation) will occur. Once symptoms appear, it is hard to imagine the consequences of delaying treatment if the patient thinks it is a minor illness, such as a bad stomach or bleeding hemorrhoids. In general, you should be careful when you have the following symptoms:

• Abdominal pain
• Change in bowel habits: sudden or gradual onset of diarrhea or constipation
• Changes in fecal morphology: such as ribbon or thin strip shape, bloody stool and mucous stools, abnormal weight loss, loss of appetite, feeling of abdominal mass
• Weak and easily tired, iron-deficiency anemia.

Causes of Colorectal Cancer

Ageing populations, westernized diets, too much meat and too little fiber are all contributing factors. According to research, eating too much fat or fatty red meat, such as beef, can increase the risk of colorectal cancer, because fats and oils produce carcinogens during cooking, as are grilled seafood and meat. Smoking triples your risk of developing colorectal cancer because the nicotine in cigarettes releases large amounts of carcinogens when burned.

Genetic variation and heredity are also important factors. Although the inherited colorectal cancer only accounts for 5% of all colorectal cancers, people whose first-degree relatives suffering from colorectal cancer have a 2-5 times higher chance of developing colorectal cancer than the general population. In addition, people aged 50 or older who are obese and have suffered from colon polyps, or ulcerative colitis or Crohn's disease, an inflammatory bowel disease, are also at high risk for colorectal cancer.

When to See a Doctor?

If your defecation habits change, or if you have the foregoing symptoms such as bloody stool, or even often feel tired, loss weight for no reason, consult a professional doctor as soon as possible.

Depending on the situation, the physician will arrange laboratory tests on fecal occult blood, hemoglobin and carcinoembryonic antigen (CEA); rectal digital examination; colonoscopy or sigmoidoscopy; lower digestive tract photography, abdominal computed tomography or abdominal ultrasound for comprehensive judgement.

Treatment

Treatment varies according to the type of tumor and the stage of cancer. Basically, surgery is the main method, while chemotherapy or radiotherapy is an auxiliary role.

The first stage of colorectal cancer can be treated with endoscopic mucosal resection. However, the treatment only works when cancer cells do not invade the muscle layer. If the muscle layer is invaded, it must be removed surgically. The tumor is surgically removed for stages 2 and 3 colorectal cancer patients, while if the tumor is too large, doctors will shrink the cancer cells with chemotherapy before performing surgery.

Recently, targeted therapy is another trend. Targeted therapy is a drug that only attacks cancer cells, unlike chemotherapy, which kills both good and bad cells. But the current targeted treatment for colorectal cancer is not effective for all patients and is expensive.