Introduction Colonic polyps are growths that could be found on the inner wall of the large intestines. These polyps have the ability to increase in size and undergo malignant changes to become colon cancer over a period of about 10-15 years. Up to 90% or more of colorectal cancers are due to malignant changes found in these polyps. Over 6000 cases of colorectal cancer are diagnosed annually in Singapore. It is second only to breast cancer in females and to lung cancer in males. The incidence of colorectal polyps is estimated to be about 20 -30% in people above 50 years old. The cause of polyps and thence cancer is still largely unknown. It is believed to be due to complex interaction between the diet/environment and the genetic constitution of the individual. There is an increased risk of colorectal cancer in individuals who have family history of colorectal cancer. This is defined as having first degree relatives with colorectal cancer diagnosed under 50 years old. There are about 5% of individuals with colorectal cancer who have familial adenomatous polypsosis (FAP). Patients with this genetic defect develop numerous polyps (>200) in the colon by the late teens and progress on to cancer by the late twenties. Signs and Symptoms Colonic polyps are asymptomatic when small and are discovered incidentally during colonoscopy. As they become larger, they may present as intermittent bleeding in the stool. Colorectal cancers may present with change in bowel habits. This may manifest as increased or decreased stool frequency and/or a change in consistency of the stool. Blood in stool is also a common symptom and must not be mistaken for piles unless proper investigations are carried out. It is essential that all bleeding in the stool must be evaluated by your doctors. Pain is not an early symptom unless there is partial obstruction by the cancer. Other symptoms are the need to strain during defaecation and anaemia. If you have family history of colorectal cancer, you should also seek screening even in the absence of these symptoms. Screening for the family must start at least 5 years younger than the age of onset of the youngest patient in the family with the cancer.

Pictures of polyp and its removal with electrical snare during colonoscopy

Investigations The best test to use for the detection of colonic polyps and colorectal cancer is the colonoscopy. Small polyps can be removed at the same time through the scope either by "hot-biopsy polypectomy" or "snare polypectomy". The other test is barium enema which involves the passage of a contrast per anum and pictures will be taken with X-rays. However, barium enema does not allow removal of polyps. The stool occult blood test (FOBT) is an effective screening tools to detect invisible traces of blood in the stool caused by a cancer or a very large polyp. A positive test would require a subsequent confirmatory colonoscopy. Treatment The treatment of colorectal polyp is removal and this will abort the cancer process and afford near complete cure. Colonoscopic surveillance after polyp removal is essential as recurrence in other sites of the large intestine is common. Larger polyps or cancer would require surgical removal. After the removal of the cancer, the intestines may often be joined back together. If this may not be possible in cancer involving the anal canal, a permanent colostomy after the surgery is required. A colostomy is a bag applied on the wall of the abdomen for the collection of faecal waste from the intestines. If there is evidence of lymph node spread on biopsy, further adjuvant chemotherapy (with or without radiotherapy) is often required to increase the chances of cure. Prognosis This is largely based on the stage or extent of the disease. The earliest stage (Dukes' A) has the cancer within the lining of the bowel wall. Dukes' B has the cancer within or through the wall of the bowel, Dukes' C is when there is evidence of lymphnodal spread and Dukes' D refers to distant, often to the liver. The respective 5-year disease free survival for the stages are >95% for A, 70% for B, 40 - 60% for C. Most patients in Dukes D succumb to their disease. The best chance of cure is when the cancer is detected early before the onset of symptoms. Thus it is important for at risk individuals to undergo regular colonoscopic surveillance (i.e. those with a family history or a personal history of colonic polyps or colorectal cancer) and for the average asymptomatic individual to undergo annual FOBT above the age of 45 years old.