Colorectal cancer is now the most common cancer in men, and 2nd most common cancer in women in Singapore. Though most colorectal cancers are thought to occur in the elderly, about 5% of cancers occur in those below age of 44 years, and 18% of colorectal cancer occurs in those below age 54.
Most people associate passing out blood or constipation with colorectal cancer. However, it is important to know that generally, bleeding or constipation does not necessarily point to cancer, and such symptoms are only exhibited by some cancer patients.
What are the symptoms?
Most family physicians are well aware of the symptoms of colorectal cancer.
Patients with right-sided colon cancer display anaemia symptoms (eg. lethargy, feeling faint and becoming easily breathless due to reduced oxygen in the body). Patients with left-sided colon cancer may see changes in bowel habits, alternating constipation and diarrhoea, and stale blood in stools. Patients with rectal cancers may experience incomplete emptying of bowels. Occasionally, patients with colorectal cancer may also have general symptoms such as abdominal discomfort, bloating, pain, or even increased flatulence.
However, early stage cancer are commonly without signs. Most polyps (benign growths) and small colorectal cancers do not usually cause symptoms. This is because these relatively smaller lesions do not obstruct stools, especially those on the right side of the colon where stools are more liquid in nature.
How to prevent or cure colorectal cancer?
In fact, the best time to prevent or to cure colorectal cancer is when there are no symptoms.
Furthermore, it is well accepted that adenocarcinoma, the most common type of colon cancer, develops in the adenoma (a type of non-cancerous growth, or benign polyp). As such, nipping any such benign polyps in the bud is tantamount to treating a future colorectal cancer.
Cancers tend to be at an early stage when detected at screening and there are more people who live at least 5 years after being diagnosed.
Colorectal cancer incidence rises rapidly from the age of 50, and the time taken for a polyp to progress to cancer may be 10 years or more. Hence, screening from the age of 40 allows for the detection of polyps and early cancers. The recent slight decrease in the incidence of colorectal cancer may be due to increased colonoscopy screening and removal of polyps.
Detecting colorectal cancer early
Stool occult blood test has been used for mass population screening. The newer tests use antibodies to accurately detect the globin component in blood. This compares favourably with the older test which detects haem in the stools – which may require dietary restrictions for up to 3 days prior to testing to ensure that the test is accurate. These stool tests are able to correctly identify or rule out the disease with 70 – 90% accuracy.
For more accurate testing, the colon can be evaluated by colonoscopy, or radiological procedures such as barium enema (also known as colon X-ray) or CT colonography (also known as virtual colonoscopy). For an optimal examination with the above procedures, the patient has to prepare their bowel, ie. to empty the colon by means of medication the night before. Though it is commonly held that colonoscopy is invasive and has a risk of puncturing the organ, radiological investigations also carry a (lower) risk of puncturing due to the fact that air has to be used to expand the colon. Colonoscopy also offers the advantage of sedation, removal of benign growths (polyps) and tissue for biopsies, and it can easily distinguish wounds from the stools sticking to them.
Surgery is a viable treatment option
Surgery still remains the mainstay of treatment of colorectal cancer. With current advancement in medical technology, laparoscopic surgery should be the standard option, with open surgery reserved for those with very large cancers or cancers that have invaded into surrounding areas. Robotic surgery may have an advantage when dealing with rectal cancers within the confined space of the pelvic cavity.
There are patients who are fretful of having a stoma, an opening to divert faeces or urine to a pouch outside the body. Creation of a temporary stoma is usually reserved for rectal tumours that are near to the anus, whereas a permanent stoma would be required if the anal sphincter is involved by the tumour and had to be removed. Temporary stomas can be closed as early as 1 month after surgery. For those patients who need a stoma, most stoma appliances can be worn discreetly and it does not leak or smell.
Chemotherapy is used after the initial treatment, for stage 3 cancers as well as stage 2 cancers that are at high risk of recurrence. Radiotherapy is used only for rectal cancers, or to relieve its symptoms and the side effects of cancer treatments.