Colorectal Cancer

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CONTENTS

Where is the colon and rectum?
What is colorectal cancer?
What are polyps?
How common is colorectal cancer (CRC)?
What is the 2nd strategy (screening for CRC)?
Who are the high risk groups?
What are the screening methods?
What is the current recommendation for screening?
How does CRC present?
How is CRC diagnosed?
How is CRC Classified?
How do we treat CRC?
What is the role of surgery?
What other treatment is necessary after surgery?
--> What is the role of radiotherapy?
--> What is the role of chemotherapy?
Supports
 
Where is the colon and rectum?

The colon and rectum (or the large intestine) is the last part of the gastrointestinal tract. Broadly our gastrointestinal tract consists of
1) oesophagus which connects the mouth to the 2) stomach where the food is stored and released periodically into the 3) small intestine where the food is broken down and absorbed. The food residue enters the 4) colon where water is absorbed and the food residue is converted to waste product by the action of bacteria. The 5) rectum is the terminal part of the colon in which the waste produce (faeces) is stored before being expelled via the anus.

What is colorectal cancer?

Our body is made up of basic units called cells. When these cells grow in an uncontrolled manner, a malignant growth or a cancer is formed.

Colorectal cancer is formed from cells which line the inner wall of the colon and rectum. This lining is called the mucosa. At this stage the cancer is termed non-invasive i.e. the cancer cells have not spread out of the colon. If undetected, the cancer will grow bigger and project into the lumen of the colon. It will also invade through the colon wall and spread via several routes:

1.
Invasion of neighboring intestines and organs.

2.
Lymphatic system into neighboring lymph glands called mesenteric lymph nodes.

3.
Blood stream to the liver where secondary malignant deposits can be formed.


Colorectal cancer that has invaded the lymph nodes or the liver are in the advanced stage.


What are polyps?

Polyps are benign lumps on the inner wall of the colon and rectum. They look like a small grape attached to the colon by a stalk. They are fairly common in people above 50 years old. Some types of polyps (called adenomatous polyps) may transform into cancer. If such polyps are detected, they should be removed to prevent the development of cancer.

Certain features of a polyp make one suspect that it may be malignant:

1. Polyp > 1cm diameter
2. Sessile polyps (i.e. polyps without a stalk)
3. Multiple polyps

How common is colorectal cancer (CRC)?

CRC is the second commonest cancer in both males and females in Singapore. About 500 Singaporeans will develop colon cancer and 300 Singaporeans will develop rectal cancer yearly. Our numbers are approaching that in developed countries such as US and England and are increasing every year.

CRC is more common in people after 50 years old. The peak incidence is people in their seventies. The Chinese has a significantly higher risk than the Malays or Indians.

What are the risk factors?

1. Males and females > 50 years old

2. Chinese has a higher risk among the races in Singapore

3. Family History

Some individuals inherit a rare disease called familial polyposis in which many colorectal polyps develop at a young age. The risk of developing CRC is very high (80 to 100%). Such individuals should consider having the colon removed before the age of 40 years old.

Another type of inheritance is an individual with a relative with polyps or CRC. He/she is also at a higher risk of CRC (although the risk is low compared to a familial polyposis individual).

4. Ulcerative Colitis (UC)

This is a disease affecting the bowels leading to inflammation and cancerous change in the long term. People with UC has a significant risk of CRC.

5. Dietary Habits

Research has identified certain types of food and food supplements which can affect our risk of CRC:


Food that increase the risk
Explanation

Meat, cooked at high temperature
It contained chemicals,
e.g. heterocyclic amines that are carcinogenic

Animal fat
Fat is converted to bile acids which can promote cancer change in the mucosa of the colon

Tobacco and Alcohol
Tobacco has been shown to increase polyp formation

Food that reduce the risk
Explanation

Fibre
(vegetables, fruits, bran)
Fibre help to reduce the transit time of faeces and to dilute the carcinogens in the colon

Vitamin Supplement (especially folate)
Studies have shown that regular multivites & folate can reduce CRC risk

Mineral intake esp calcium
Calcuim can bind to fatty acids and bile acids and reduce our risk.

6. Drugs
Current users of HRT (hormone replacement therapy) are at a lower risk of CRC and this protection disappear within 5 years of stopping the HRT.

Aspirin and NSAID (a strong painkiller drug) are known to reduce the risk from CRC. However it is too early at this stage of research to recommend the routine use of these drugs for this purpose.

7. Sedentary lifestyle and obesity
These two related factors increase the risk of CRC. Physical Activity helps to regulate the transit time of faeces in the colon and hence can reduce the risk.

8. Past history of colorectal polyp or colorectal cancer.

Despite knowing all these risk factors, the exact cause of CRC remains unknown. It is estimated that 50% of CRC patients have no known risk factors.

How to prevent CRC?

There are two strategies to prevent CRC.

The 1st strategy is to reduce our risk by eliminating the risk factors. From the list of risk factors we can see that by adopting certain lifestyle habits, an individual can reduce significantly his/her risk.

1. Take a diet rich in vegetable, fruits and fibres. Our Ministry of Health (MOH) recommends 5 or more servings of vegetables and fruits daily, each serving is ? cup.

2. Reduce intake of red meat especially cooked meat. An average adult should be restricted to 2 servings or less of meat and alternatives daily; (1 serving – 1 piece (palm size) of meat, fish or poultry.

3. Reduce intake of fat especially animal fat to less then 30% of total energy intake

4. Exercise regularly 2 to 3 times per week for ? to 1 hour duration. Exercises include jogging, brisk walking, swimming, bicycling. The intensity of the exercise should leave one mildly breathless.

5. Take a multivitamin supplement which include folate & calcium regularly

6. Cut down on smoking!

7. Cut down on alcohol!

8. If above 45 years old, go for an annual health check to detect colorectal polyps or cancer.

What is the 2nd strategy (Screening for CRC)?

The second strategy is to identify the high risk group and keep them under regular reviews to detect colorectal polyps and cancer. There is strong evidence to suggest that CRC develop from polyps. Hence by getting rid of polyps we can prevent CRC. Regular screening can also detect the CRC at an early stage and with effective treatment such patients can survive longer.

Who are the high risk groups?

1.
Any male or female, above 45 years old and especially of Chinese descent among the races in Singapore

2. Family history of colorectal cancer
3. Family history of colorectal polyp
4. History of Ulcerative Colitis
5. Past history of CR polyp or CRC

What are the screening methods?

Faecal occult blood test (FOBT) : This is one of the most simple screening test and is based on the fact that colorectal polyps and cancers can bleed into the colon. The amount of bleeding can be very small and not visible (hence occult). It can be detected by special tests on the faeces.

The test is available in a kit with instructions. The person takes it home and follows the instructions to sample the stools for occult blood (OB). If OB is present, he/she has to undergo further investigations such as colonoscopy or barium enema to exclude a polyp or cancer. This is because OB can be also due to piles, colitis or other non-cancerous conditions.

Conversely if OB is absent, it does not mean that a person is entirely free of colorectal polyp or cancer as the test is not 100% accurate. E.g. eating partially cooked meat or certain foods can affect the test and cause a false positive result.

However, with newer methods for detecting OB, FOBT is now more accurate and recent research has shown that it can detect colorectal polyps and early colorectal cancers.

Digital rectal examination: This is routinely performed by the physician during clinical examination. As the finger can only reach the anus and lower rectum, it can only detect 10% of CRC.

Flexible sigmoidoscopy or colonoscopy. This test involves the examination of the colon & rectum using a flexible fiber optic instrument introduced in the anus. The patient is under sedation and can experience abdominal discomfort. When the examination is limited to the sigmoid colon (left colon) it is called sigmoidoscopy and if it involves the whole colon it is called colonoscopy. In addition to its diagnostic use, the colonoscopy can be used for treatment e.g. remove polyps, biopsy cancerous lumps, inject bleeding spots. Colonoscopy is a safe procedure with a low incidence of complications.

Double contrast Barium Enema X-ray. This is a special x-ray examination of the colon & rectum and its accuracy is equivalent to that of colonoscopy. The disadvantage is that if a polyp or a cancer is detected, a colonoscopy is needed to biopsy it. Its advantages over the colonoscopy are 1) less expensive 2) better at locating the polyp or cancer 3) less complications.


What are the current recommendations for screening?

Beginning at age 45 to 50 years

Have a faecal occult blood test yearly
Have a sigmoidoscopy every 5 years
Or a colonoscopy every 10 years
Or a barium enema x-ray every 10 years
A digital rectal examination is performed every 5 to 10 years

Those in the high risk group should have screening earlier and/or more frequently.

Polyps found on screening should be excised to prevent transformation to CRC.

How does CRC present?

A patient with CRC often has symptoms only when the cancer is advanced and these symptoms can be varied. The following are the common symptoms:

1. Change in bowel habits. A colon cancer can cause partial obstruction of the colon leading to “holdup’ of faeces and a delay in passing motion. It can also irritate the colon resulting in frequent loose stools. In short, a person with a change in bowel habits of more than 6 to 8 weeks should consult a doctor.

2. Rectal bleeding. A rectal cancer can present with fairly fresh bleeding separate from faeces due to its proximity to the anus. It can be mistaken for bleeding from piles. Bleeding from colon cancer is usually darker and mixed with the stools. Rectal bleeding is a serious symptom and must be investigated especially in individuals above 40 years old.

3. Abdominal distension and discomfort. This is a vague symptom which can also be due to other abdominal problems e.g. irritable bowel syndrome, gallstones.

4. Difficulty or pain during defaecation. This applies to rectal cancer which obstructs the passage of faeces and considerable force is needed to pass motion. There is also a painful sensation of incomplete emptying called tenesmus due to the presence of a tumour in the rectum.

5. Presence of anaemia and weight loss. Anemia is often associated with a right sided colon tumour which has bled unnoticed for a long time (occult bleeding). Anaemia may result in giddiness, weakness & fainting spells. Significant unexplained weight loss can be often due to a serious illness e.g. cancer.

6. Presence of an abdominal mass. A right sided colon cancer can present with an abdominal mass which is uncomfortable and detected by the patient.

7. Colorectal cancer can present acutely as an emergency in two situations:
a. Bowel perforation. An advanced CRC can erode through the colon wall and cause a perforation with leakage of faeces causing peritonitis and septicaemia.
b. Bowel Obstruction. Left sided colon cancer often grows around the colon and cause total obstruction. The patient complains of constipation, abdominal distension and vomiting over a period of few days. An emergency operation is required.
Both acute presentations are associated with poor survival even after treatment of the CRC.

How is CRC diagnosed?

History:
From the list of symptoms discussed, a physician can roughly suspect whether a patient has CRC and whether to proceed with further investigations. The physician can also determine whether the patient is a low or high risk individual.

Physician examination: Important signs to look for:
1. Significant anaemia
2. Significant weight loss
3. Swollen lymph nodes in the left neck
4. Abdominal lump
5. A lump on digital rectal examination

Investigations that are essential to diagnose a patient with CRC include:
1. Colonoscopy. In addition to diagnosing a CRC it can also check the entire length of the colorectum for a second cancer or the presence of polyps. At the same time a cancer can be biopsied for histology and polyps can be removed.

2. Double contrast barium enema x-ray. Accuracy is equivalent to that of colonoscopy but lesions found cannot be biopsied or removed via this method.

3. CT Scan Abdomen. This expensive computerized x-ray scan can reveal internal organs and intestines in very good detail. It is especially useful for determining the actual extent and location of the tumour, invasion of adjacent organs or bowels and the presence of liver metastases. An alternative to CT Scan is an ultrasound scan which is cheaper. Ultrasound Scan is accurate for diagnosing liver metastases.

4. Tumour markers are substances found in the blood that are specific for a type of cancer. For CRC, the tumour marker is carcino-embryonic antigen (CEA) i.e. patients with CRC may have a high level of CEA. CEA is useful in monitoring patients for recurrence after surgery.

5. Biopsy of tumour. A diagnosis of cancer is based on a biopsy of the tumour. In this procedure a piece of the tumour is removed and sent to the laboratory where it is examined under the microscope.

How is CRC classified?

Broadly speaking CRC can be classified according to the extent of their spread – stage and grade

Stage – CRC is classified in 4 stages called TNM stage 1 to 4.

Stage Average Survival (%)
1. Small cancer within bowel wall
80
2. Cancer invaded onto the outer surface of the colon wall or adjacent organs
60
3. Neighbouring lymph nodes infiltrated by cancer
40
4. Distant metastases e.g. liver metastasis
20

Grade is a measure of aggressiveness of the cancer cells and there are 3 grades, grade 1 (well differentiated, least aggressive), grade 2 (moderately differentiated) and grade 3 (poorly differentiated, most aggressive). Most CRC are in grade 2.

Both the stage and grade is vital in estimating the survival of the patient and in deciding the treatment needed.

Both the stage and grade can only be accurately determined from examination of the tumour specimen under the microscope after surgery.

How do we treat CRC?

There are 3 main methods:

1) Surgery 2) Radiotherapy 3) Chemotherapy

What is the role of surgery?

Surgery is the main form of treatment for CRC. The aim is complete removal of the cancer with a length of normal bowel and its mesenteric lymph nodes. The 2 ends of the bowel are joined back (anastomosis). For a colon cancer, it is called a Hemicolectomy Operation, for a rectal cancer it is called an Anterior Resection.

For rectal cancers situated closed to the anus, complete clearance of the cancer involves removing the anus as well. The operation is called an AP Resection. The patient will have a colostomy in the right lower part of his abdomen in which the colon is attached to the skin and a new opening created for the discharge of faeces. The patient has to wear a colostomy bag to receive the faeces and learn how to take care of the opening and surrounding skin.

In some situations, a colostomy is temporary to divert the faeces while allowing anastomosis to heal. The colostomy is closed at a second operation.

In order to avoid a permanent colostomy, new surgical techniques have evolved to retain the anus. The first method is to perform intestinal anastomosis as close to the anus as possible using mechanical staples rather than hand sewn stitches (sphincter saving surgery). The second method is to create a ‘new anus’ using muscles from the thigh (neo-sphincter surgery)

Surgery in special situations:
1.
Liver metastasis. In a fit patient with few isolated liver metastasis, removal of these metastasis can be performed at the same time as excision of the CRC. However this is not possible most of the time and patient with a CRC with liver metastasis is treated by chemotherapy.

2.
Large inoperable CRC. In order to relief bowel obstruction, an intestine bypass surgery is required.

3.
CRC causing intestinal obstruction or perforations. In this acute situation, the patient is very ill and emergency surgery is required to relieve the obstruction or deal with the leakage of faeces. When the patient has recovered, a 2nd or even 3rd operation maybe necessary to remove the tumour and join back the intestine (staged operation).


Laproscopic colon surgery (also known as keyhole surgery). CRC has been removed using such minimally invasive technique and the advantage is faster post-operative recovery with less pain. However it is technically difficult, time consuming and expensive. There maybe an increase in the risk of cancer implantation into the skin. At this stage this technique is under clinical evaluation.

Pre-operation preparation. As CRC surgery is a major operation, careful preoperative preparation is of utmost importance.

1. Individuals more than 70 years old or with chronic ill health (heart or lung problems, diabetes, hypertension, strokes, liver or kidney problems) are at high risk from surgery and general anaesthesia. They are assessed carefully for fitness for surgery and general anaesthesia with clinical examination and investigations (chest x-ray, ECG, blood tests).

2. Preparations
Patient
  Pre-operation Preparation

Smoker with poor lung function
Stop smoking, breathing exercises

Ischaemic heart disease on antiplatelet therapy
Cardiac assessment, stop anti platelet drugs

Poor liver function with low blood albumin
Albumin transfusion

Hypertension or diabetes mellitus
Careful control BP or blood sugar before operation


3. Bowel “preparation”. All faeces have to be cleared out of the colon preoperatively to prevent contamination at the time of surgery. Patient is admitted before the operation and given purgatives. They are also allowed only liquid low fibre diet for a few days before operation.

4. Antibiotic cover. As colorectal surgery involves coming into contact with faeces, a strong antibiotic is administered before the operation.

Immediate post-operation period. This crucial period which is about one week long is when the patient recovers from the operation. He may develop a complication such as lung infection or leakage from the anastomosis and may die from it. He is on an intravenous drip which supplies him with fluids. After he recovers his intestinal function and is able to eat and drink, the intravenous drip is stopped. Medications needed during this period include antibiotics and a strong painkiller.

What other treatment is necessary after surgery?

What is the role of radiotherapy?

Radiotherapy is the administration of powerful radioactive rays to treat cancer. Its role in the treatment of CRC is secondary to surgical excision and is used in the following situations:

1. After surgical removal of a rectal cancer which has invaded the adjacent organs and/or nearby lymph nodes with the intention of mopping up residual cancer cells within the site of the cancer.

2. Preoperatively to a locally advanced rectal cancer to shrink it to a size where it can be surgically removed.

Radiotherapy is administered in daily sessions, 5 days per week over 4 to 6 weeks. Side effects are usually tolerable & temporary; abdominal cramps & pain, constipation or diarrhoea, cystitis, excoriation of perianal skin and generalized tiredness.

What is the role of chemotherapy?

Chemotherapy is the administration of toxic drugs to kill cancer cells which may be found at the site of the cancer or elsewhere in the body after surgery. It is indicated for patients with advanced CRC e.g. stage II, III or IV after surgery and it improves their chance of survival. The chemotherapy usually involves weekly injection of a cytotoxic drug called 5FU (5 Flurouracil) alone or in combination with other drugs for up to a year.

Because of its toxicity, chemotherapy also causes significant side effects. The immediate side effects include nausea, vomiting, diarrhoea, suseptibility to infection, low white cell counts, hair loss. The long-term side effects include premature menopause, risk of a 2nd cancer.

Support Groups

1.

Ostomy Club
This club is one of the Singapore Cancer Society’s rehabilitation group, with the aim to reach out and help new osteomates to cope and adjust to a new lifestyle. Monthly meetings are held at the Singapore Cancer Society. For more information regarding the Ostomy Club, please call 221-9577

2.
Oncology Support Group

The Oncology Support Group is a self-help group for patients undergoing chemotherapy, radiotherapy or surgery for cancer, organized primarily by cancer patients themselves.

Facilitated by trained oncology nurses and ex-patients, the Group offers interactive sessions aimed at easing the stress of a cancer diagnosis and subsequent treatment.

Open to both cancer patients and their family members, each session is an opportunity for participants to interact with ex-patients and to ask questions concerning their illness. For example, information on how to cope with the side effects of treatment will be discussed.

It must be emphasized, however, that the Oncology Support Group is not an avenue for seeking a second opinion on your treatment plans and / or options.

The aim of the Group is to offer patients the opportunity to voice their thoughts – whether it be frustrations or fears – and for them to be able to draw on the experiences and coping strategies of patients who have gone on to the road to health again. The bowel is the last part of the digestive tract, which consists of a small bowel and a large bowel. The large bowel has 2 parts, namely the colon and the rectum, hence the term colo-rectal.

When cells in the inner wall of the bowel become abnormal and divide without control or order, a tumour mass is formed. As it grows, the tumour can narrow or block the bowel. The cancer can spread through the bowel wall, and then spread to nearby lymph nodes, and finally to other parts of the body.

Q: How common is colorectal cancer?

In spore, colorectal cancer is the 2nd most common cancer, after lung cancer in male and breast cancer in female. Cancer is extremely uncommon in small intestines.

Q: What causes colorectal cancer?

As with other cancers, certain people are more likely to develop colorectal cancer. The risk increases after the age of 40 and if one is on a high fat-low fibre diet. Personal history, inflammatory bowel diseases, smoking, lack of exercise, lack of calcium in food, alcohol consumption, & family history are other risk factors associated with this disease.

Q: What are the signs & symptoms of colorectal cancer?

Early detection of colorectal cancer is important, as the chances of cure are the greatest at early stage. Medical attention should be sought if the following symptoms persist:

. Rectal bleeding or blood in the stool
. Stools that are smaller in width than usual
. Diarrhoea or constipation
. Abdominal discomfort with feeling of bloating, fullness or cramps
. Frequent gas pains
. A constant urge to pass stool
. Constant tiredness & unexplained weight loss

Q: How is colorectal cancer detected?

The diagnosis may involve digital examination by a doctor for any swelling or lump inside the anus. A stool test for occult blood is able to detect more than 70% of colorectal cancer at an early stage. A narrow tube, called a sigmoidoscope, may be used to inspect the rectum. Alternatively, a colonoscopy may be performed to inspect the entire length of the bowel, and to remove benign growths. A biopsy may be done during the sigmoidoscopy or colonoscopy for microscopic examination. At times a barium enema is done to check for abnormalities in the bowel.

To confirm the findings of these tests, further tests such as ultrasound scan and CT scan are performed.

Q: What are the treatment methods for colorectal cancer?

All the 3 conventional methods, namely surgery, chemotherapy & radiotherapy have been used on colorectal cancers.

Surgery involves the removal of that part of bowel containing the cancer as well as the lymph glands in the abdomen. The 2 open ends are then joined together. If the bowel cannot be rejoined, then an artificial opening, called a stoma, is opened onto the abdominal wall. A stoma bag is placed over the stoma to collect the bowel motions. In most cases, the colostomy is only temporary.

Chemotherapy is useful for cancer that has spread to the lymph nodes and when cancer has spread too far for surgery to be effective. It is used as palliative treatment to relieve pain rather than for cure.

Radiotherapy is recommended for rectal cancer to improve control of cancer.

Living with colostomy

Before surgery, it is necessary to be informed of the practical and personal aspects of living with a colostomy. There may also be certain food, such as high fiber food, which one has to avoid because these may give loose stools and produce wind. Having a colostomy, however, should not affect one's ability to have sexual relations.

The Singapore Cancer Society has a support group under the name of "Stoma Club"
  Early detection can safe your life, chances for early treatment can be much easier and lower treatment cost.

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