About Colorectal Cancer:
- Colon cancer is the most common cancer in Singapore – more than 1000 patients diagnosed each year
- Age-standardized incidence rates are 35.1/100,000/yr in men and 29.9 in women, more than twice that of the next SEA country
- Rates have been increasing at a startling average annual rate of approximately 2.6% for men and 2.35% for women
- Colon cancer causes 19% of all cancer deaths in men and 14% in women
- Dramatic improvements in survival and cure rates from 36 to 66% in men, 32 to 71% in women
◦Early detection◦Advances in surgery and chemotherapy
What is cancer of the Colon and Rectum?
The colon is the part of the digestive system where the waste material is stored. The rectum is the end of the colon adjacent to the anus. Together, they form a long, muscular tube called the large intestine (also known as the large bowel). Tumors of the colon and rectum are growths arising from the inner wall of the large intestine. Benign tumors of the large intestine are called polyps. Malignant tumors of the large intestine are called cancers. Benign polyps do not invade nearby tissue or spread to other parts of the body. Benign polyps can be easily removed during colonoscopy and are not life-threatening. If benign polyps are not removed from the large intestine, they can become malignant (cancerous) over time. Most of the cancers of the large intestine are believed to have developed from polyps. Cancer of the colon and rectum (also referred to as colorectal cancer) can invade and damage adjacent tissues and organs. Cancer cells can also break away and spread to other parts of the body (such as liver and lung) where new tumors form. The spread of colon cancer to distant organs is called metastasis of the colon cancer. Once metastasis has occurred in colorectal cancer, a complete cure of the cancer is unlikely.
Globally, cancer of the colon and rectum is the third leading cause of cancer in males and the fourth leading cause of cancer in females. The frequency of colorectal cancer varies around the world. It is common in the Western world and is rare in Asia and Africa. In countries where the people have adopted western diets, the incidence of colorectal cancer is increasing.
How common is Colorectal Cancer?
Colorectal cancer is now the commonest cancer in Singapore. It affects males and females alike. Between 1993 and 1997, about 4899 cases were diagnosed in Singapore.
What is the Age of Onset for Colorectal Cancer?
Most persons diagnosed with colorectal cancer are older than 45 years of age. Younger persons, less than 20 years of age, diagnosed to have colorectal cancer must be suspected to have a hereditary form of colorectal cancer, such as familial adenomatous polyposis.
What are the Risks and Causes of Colon Cancer?
Doctors are certain that colorectal cancer is not contagious (a person cannot catch the disease from a cancer patient). Some people are more likely to develop colorectal cancer than others. Factors that increase a person’s risk of colorectal cancer include high fat intake, a family history of colorectal cancer and polyps, the presence of polyps in the large intestine, and chronic ulcerative colitis.
Much has been discussed regarding the role of dietary factors and colorectal cancer. There are suggestions that diets high in animal fat, red meat and low in fibre increase the risk of colorectal cancer.Persons considered to be at high risk of colorectal cancers are persons with a history of colorectal polyps, previous history of colorectal cancer, persons with one immediate relative diagnosed to have colorectal cancer before the age of 45 years, persons with two or three immediate relatives diagnosed with colorectal cancer at any age, or persons with a family known to have familial adenomatous polyposis.
What are the symptoms of Colon Cancer?
Symptoms of colon cancer are numerous and nonspecific. They include fatigue, weakness, shortness of breath, change in bowel habits, narrow stools, diarrhea or constipation, red or dark blood in stool, weight loss, abdominal pain, cramps, or bloating. Other conditions such as irritable bowel syndrome (spastic colon), ulcerative colitis, Crohn’s disease, diverticulosis, and peptic ulcer disease can have symptoms that mimic colorectal cancer. For more information on these conditions, please read the following articles: Irritable Bowel Syndrome, Ulcerative Colitis, Crohn’s Disease, Diverticulosis, and Peptic Ulcer Disease.
Colon cancer can be present for several years before symptoms develop. Symptoms vary according to where in the large bowel the tumor is located. The right colon is spacious, and cancers of the right colon can grow to large sizes before they cause any abdominal symptoms. Typically, right-sided cancers cause iron deficiency anemia due to the slow loss of blood over a long period of time. Iron deficiency anemia causes fatigue, weakness, and shortness of breath. The left colon is narrower than the right colon. Therefore, cancers of the left colon are more likely to cause partial or complete bowel obstruction. Cancers causing partial bowel obstruction can cause symptoms of constipation, narrowed stool, diarrhea, abdominal pains, cramps, and bloating. Bright red blood in the stool may also indicate a growth near the end of the left colon or rectum.
What tests can be done to detect Colon Cancer?
The simplest way to detect a rectal cancer is by insertion of the doctor’s finger into the rectum, i.e. a rectal examination. This can be done in the outpatient clinic, takes less than 5 minutes and causes minimal discomfort. However, this detects cancers only in the last 5 to 8 cm of the rectum.When colon cancer is suspected, either a lower GI series (barium enema x-ray) or colonoscopy is performed to confirm the diagnosis and to localize the tumor.
A barium enema involves taking x-rays of the colon and the rectum after the patient is given an enema with a white, chalky liquid containing barium. The barium outlines the large intestines on the x-rays. Tumors and other abnormalities appear as dark shadows on the x-rays. For more information, please read the Lower Gastrointestinal Series (Barium Enema) article.
Colonoscopy is a procedure whereby a doctor inserts a long, flexible viewing tube into the rectum for the purpose of inspecting the inside of the entire colon. Colonoscopy is generally considered more accurate than barium enema x-rays, especially in detecting small polyps. If colon polyps are found, they are usually removed through the colonoscope and sent to the pathologist. The pathologist examines the polyps under the microscope to check for cancer. While the majority of the polyps removed through the colonoscopes are benign, many are precancerous. Removal of precancerous polyps prevents the future development of colon cancer from these polyps. For more information, please read the Colonoscopy article.
If cancerous growths are found during colonoscopy, small tissue samples (biopsies) can be obtained and examined under the microscope to confirm the diagnosis. If colon cancer is confirmed by a biopsy, staging examinations are performed to determine whether the cancer has already spread to other organs. Since colorectal cancer tends to spread to the lungs and the liver, staging tests usually include chest x-rays, ultrasonography, or a CAT scan of the lungs, liver, and abdomen.
Physical examination by the doctor of the neck, chest and abdomen are important as colorectal cancers can spread to lymph glands in the neck, to the lung and to the liver. Blood tests may also be helpful in certain circumstances.
Once cancer is confirmed, x-rays or scans of the lungs and scans of the liver are required before further treatment is advised.
How can Colon Cancer be prevented?
Unfortunately, colon cancers can be well advanced before they are detected. The most effective prevention of colon cancer is early detection and removal of precancerous colon polyps before they turn cancerous. Even in cases where cancer has already developed, early detection still significantly improves the chances of a cure by surgically removing the cancer before the disease spreads to other organs. Multiple world health organizations have suggested general screening guidelines.
What is the treatment option of Colon Cancer?
The mainstay of treatment is surgery. The cancer, its surrounding fat and lymph glands are removed in one piece. The two ends of the cut section are joined together. During surgery, the surgeon will normally inspect the liver and other surrounding organs for signs of cancer as well.
Depending on the stage of the cancer, chemotherapy may be required after surgery to improve a person’s chance of cure from cancer. Chemotherapy involves injections of cancer killing medicines into a vein on the hand. Chemotherapy, which usually lasts 6 months, is usually associated with mild mouth ulcers, mild diarrhoea, mild hair loss, possible darkening of complexion, and nausea. The commonest medicines used are 5- fluorouracil and newer drugs such as Oxaliplatin.
What is the treatment option of Rectal Cancer?
Again, the mainstay of treatment is surgery. Because of the position of the rectum in the bony pelvis, the chance of cancer spreading to the surrounding organs, such as bladder, uterus and bone, is high. Even if the cancer was totally removed by surgery, occasionally there is concern that undetectable cancer cells may lie in the vicinity since the distance between cancer and normal tissue is so short. Hence, depending on how far the cancer has invaded surrounding fat and organs, and other factors, radiotherapy may be required after surgery to improve a person’s chance of remaining free from rectal cancer.
Radiotherapy involves giving high-energy rays into a small area where the original cancer was. The course of treatment, given daily for 5 minutes, usually lasts 5 to 6 weeks. Side effects which may occur include diarrhoea, tiredness, skin redness and rash. In some women, radiotherapy brings on early menopause.
As with colon cancer, chemotherapy may also be required after surgery. Radiotherapy may be given together with chemotherapy.
Prognosis of Colorectal Cancer
Prognosis means the probable outcome of an illness based upon all the relevant facts of the case. All findings from clinical examination and x-ray investigations and pathology reports are important and must be considered together to decide what the progress of an individual case of Colorectal cancer may be. From this, the appropriate course of treatment can be decided and put into action. The treatment strategy will vary from person to person. With prompt and appropriate treatment, the outlook for a person with early Colorectal cancer is good.
The doctor looks for the following features:
- The site of the large intestine cancer is important. This will determine what type of surgery is required and whether a stoma is likely to be created. This will also determine if radiotherapy is required after surgery.
- How many of the lymph glands in the mesentery were involved? The more lymph glands involved, the more likely the cancer will recur. When lymph glands are involved, chemotherapy is usually recommended to improve a person’s chance of cure.
- Did the cancer involve other organs? In the presence of advanced disease, chemotherapy and occasionally radiotherapy improves a person’s quality of life, prolonging the time to further growth of the cancer and overall survival. New drugs are being developed every few years. Some of these drugs may already be available in a clinical study being run at your centre. Ask your doctor for more information.
Screening for Colorectal Cancer
Cancer screening aims to detect the cancer or its precursors (i.e. colonic polyps) before the onset of symptoms. We do know that with earlier detection coupled with timely surgery, there is a higher chance of cure.
The following recommendations are adapted from the Ministry of Health, Singapore guidelines:
Screening recommendations for the average risk
- Faecal Occult Blood Test (FOBT) – annually
FOBT detects human haemaglobin from digested blood in the faeces. As the tests are not very sensitive, several stool samples are required, and the tests should be done annually.
- Flexible sigmoidoscopy – 5 yearly
This procedure is similar to the colonoscopy except that only the left side of the large bowel is examined. Its benefit is that it is a shorter procedure, and easier to perform, with very low risk. It is therefore useful in the population with average risk of colon cancer, and is used in adjunct with the FOBT.
- Colonscopy – 10 yearly
This is the gold standard in large bowel evaluation. In this procedure, a tube with a camera is inserted through the anus and is navigated through the entire large bowel. This procedure is usually done as a day case under light sedation. Its main advantages are that it is very sensitive, and abnormalities excountered can be biopsied or removed straight away. Risks are very low.
Bowel cleansing is performed the day before the colonoscopy, and involves drinking a solution that clears the bowel. This is necessary as stool residue in the large bowel can obscure small lesions.
- Double-contrast Barium Enema
This is a radiographic procedure where a dye is inserted via the anus into the large bowel. This dye outlines the large bowel. Serial X-rays are taken of the abdomen, and large lesions or tumours in the wall of the bowel can be detected. It is not as invasive a procedure as colonoscopy. Unfortunately, it is a less sensitive test, and takes longer to complete. Patients who have a positive test will still need to undergo a colonoscopy to obtain tissue for examination.
Recommendations for screening people with increased risk
1. Familial adenomatous polyposis coil (FAP):
- start at puberty (10-12 years)
2. Hereditary non-polyposis colorectal cancer (HNPCC):
- every 1-2 years from 20 years old or 10 years before youngest age of diagnosis in the family
3. Individuals with history of adenomatous polyps and resected colorectal cancer:
- annual scope till free of polyps and subsequent 3 yearly scopes
4. People with family history of colorectal cancer or adenomatous polyps:
Start at 40 years
- first degree relative < 60 years old or 2x first degree relatives
- first degree relative > 60 years old or 2x second degree relatives
Population risk (start at 50 years)
- 1 x second degree relatives or third degree relatives
There are now newer methods of colorectal screening including virtual colonoscopy which makes use of existing spiral CT scan technology and performs fine-cuts CT scanning and reconstruct the colon with a software programme. This allows a 3-dimensional examination and allows a “fly-through” effect just like performing a colonoscopy in the examination of mucosal lesions.
Frequently Asked Questions about Colorectal Cancer
1. I have haemorrhoids. Will these become cancerous?
Haemorrhoids are enlarged blood vessels of the rectum. They arise because of constipation or pregnancy. They do not become cancerous. However, they will bleed from time to time and over the years may cause anaemia or a lack of red blood cells which may cause symptoms such as tiredness and breathlessness. Haemorrhoids which are bleeding, itching or discharging mucus, should be attended to by a professional. Any bleeding from the back passage requires investigation and should not be assumed to be hemorrhoidal in origin.
2. My father / uncle was diagnosed to have large intestinal cancer?
Am I at higher risk?
Persons considered to be at high risk of colorectal cancers are persons with a history of colorectal polyps, previous Colorectum cancer, persons with one immediate relative diagnosed to have Colorectal cancer before the age of 45 years, persons with two or three immediate relatives diagnosed with colorectal cancer at any age, persons with a family member known to have familial adenomatous polyposis.
Any patient with familial adenomatous polyposis is usually informed by his surgeon to send the rest of his family for screening. This is a hereditary condition where hundreds and thousands of polyps develop in the colon, rectum and occasionally stomach. It is usually present by the teenage years. The risk of developing colorectal cancer from one of these polyps is very high. Very often, the affected person has his colon removed before development of colon cancer. He or she can still lead a normal life after surgery. The diagnosis of familial adenomatous polyposis is usually made on sigmoidoscopy or colonoscopy. Recently, a blood test has been developed that can detect the abnormal gene responsible for this condition.
Persons considered to be at high risk for developing colorectal cancer should consider colonoscopy every 3 years. Persons with a history of colonic polyp should consider colonoscopy and removal of polyps every year until no new polyps develop. Thereafter colonoscopy should be performed every 3 years.
3. I am afraid of Colorectum cancer. Should I go for screening?
If you are worried about colorectal cancer, you can discuss the possibility of faecal occult blood testing with the general practitional. The most effective screening test is colonoscopy, which is recommended in some countries for routine screening of individuals aged 50- 70 every 3 years.
4. I have been diagnosed to have colorectal cancer. How long will I live?
Many people who have had colorectal cancer live a normal lifespan. Present treatments offer a good prognosis but you may require several types of treatment to have the best chance of avoiding recurrence of the cancer.