Colorectal Cancer in Malaysia
05 April 2019
Introduction
The colon is the large intestine with the rectum being the last part of the large intestine. Colorectal cancer is a malignant growth that occurs in either the colon or rectum. Colorectal cancer is today the most common cancer in men and third most common cancer in women in Malaysia. Overall, men are only a little more likely than women to develop colorectal cancer. The most common type of colorectal cancer is the adenocarcinoma. Most of these colorectal cancers start as small growths called polyps. The polyps can be single or multiple, flat or stalked, small or large.
Patient Factors
There are several important risk factors associated with the development of colorectal cancer. Race and sex are the more common mentioned factors. The Chinese being more likely to develop colorectal cancer compared to Malays and Indians.
| Men | Women | |
|---|---|---|
| Chinese | 31.5 | 26.2 |
| Indian | 15.7 | 12.9 |
| Malay | 12.3 | 9.7 |
Malaysian colorectal cancer rates per 100,000
A previous history of colorectal polyps or cancer increases your risk of colorectal cancer. Other than increasing age, obesity and physical inactivity have also been cited as risk factors in the development of colorectal cancer. A history of inflammatory bowel disease, diabetes or previous radiation therapy can increase your risk of colorectal cancer.
Genetic factors are important, in particular a family history of colorectal cancer, breast cancer, ovarian cancer and endometrial cancer. Inherited conditions such as familial adenomatous polyposis (FAP) and hereditary non-polyposis colorectal cancer (HNPCC) also increase the risk of colorectal cancer in patients.
It is important to note that most cases of colorectal cancer do not have an identifiable genetic risk factor.
Normal Colon
Colon Polyp
Colon Cancer
Environmental Factors
Increased intake of red meat, in particular cooked red meat as well as an increased intake of total calories have been implicated to increase the risk of colorectal cancer development. While a protective effect is seen with consumption of greater amounts of dietary fibre. Fruits and vegetables besides their fibre content, contain a number of antioxidants and other anticancer compounds giving an additional protective effect. Smoking and alcohol consumption also increase your risk of colorectal cancer.
Clinical Features
While most patients with colorectal cancer present with some symptoms, a significant number of patients may have none. The more common features include:
- • Rectal bleeding
- • Altered bowel habit
- • Passage of small calibre stools
- • Persistent abdominal discomfort
- • Excessive flatulence
- • Abdominal mass
- • Feeling of incomplete emptying of bowel motion
- • Weight Loss
Any person with the above symptoms should see a doctor for further assessment.
Investigations
The gold standard in colorectal cancer investigation is the colonoscopy. This is where a small flexible fibreoptic scope is inserted through the anus to visualise the entire colon and rectum. Through the colonoscope, polyps can be removed, suspected tumors can be biopsied and bleeding can be stopped.
A CT colonoscopy is essentially a virtual colonoscopy that is done using the CT scan. However there are limitations such as it being unable to biopsy or remove polyps.
A barium enema is now rarely performed as colonoscopy completion rates are so high.
Tumor markers in the form of blood CEA levels to detect colorectal cancer are not accurate as they have a low sensitivity and low specificity. However, recent advances to look at molecular genetics from a blood test (colonsentry) to assess risk of colorectal cancer development is promising.
Staging of colorectal Cancer
Once diagnosed with colorectal cancer, the cancer is the further assessed with imaging techniques such as an endorectal ultrasound, CT scan or an MRI scan. To assess the spread of the tumor, a PET/CT scan can be performed. These investigations help to stage the colorectal cancer, though in many cases the staging is done after surgery. In general, there are 4 stages to colorectal cancer:
| Stage 1: | The cancer is within the lining of the colon |
| Stage 2: | The cancer has spread through the thickness of the entire colonic wall |
| Stage 3: | The cancer has spread to the lymph nodes |
| Stage 4: | The cancer has spread to distant organs such as liver or lungs |
Management
The main aspects of treating the colorectal cancer includes surgery, chemotherapy and radiotherapy. Factors determining the modalities used will depend on the site of the cancer, size of the cancer and stage of the cancer.
Surgery
Surgery involves the removal of the cancer by cutting the cancer out. This can be done through the colonoscope for small cancers, keyhole (laparoscopic) surgery or open surgery for larger cancers. When part of the large intestine has been removed, the remaining intestine will be re-joined to allow the patient to pass motions normally. Sometimes a temporary colostomy bag may be required to allow healing to take place, and rarely a permanent colostomy bag is necessary.
Chemotherapy
Chemotherapy is the use of special drugs to kill cancer cells. This can be given as tablets or injections or in an infusion. Chemotherapy is usually necessary in stage 3 and beyond colorectal cancer. The chemotherapy can sometimes be given before surgery to shrink the tumor size prior to surgery. Targeted therapy is the use of specialised drugs that target specific areas of the cancer cell to kill the cancer cell.
Radiotherapy
Radiotherapy is the use of strong x-rays to help kill any cancer cells. Radiotherapy can be used either before or after surgery and can also be used together with chemotherapy. Radiotherapy is used usually for treating rectal cancer.
Preventing Colorectal Cancer
First and foremost, make changes in your lifestyle. These would include:
- Increase intake of fruits and vegetables
- More fibre in your diet
- Exercise regularly
- Maintain a healthy weight
- Stop smoking
- Alcohol in moderation
For those who are at average risk, a screening colonoscopy is advised from the age of 40 years. Earlier for those with high risk such as a strong family history of colorectal cancer.
Back
