Many people associate colorectal cancer as a death sentence, where one has to pass stools through a stoma that is leaking and giving off bad smells, while awaiting the disease to progress before they eventually die.
Colorectal cancer is now the most common cancer in men, and the second most common cancer in women in Singapore. Although the incidence was rising rapidly in the last century, it seems to have plateaued since the early 2000s. Though most colorectal cancers are thought to occur in the elderly, about 5% of cancers occur in those below the 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 most patients who see me for bleeding or constipation do not have cancer, and that only some cancer patients have bleeding or constipation.
Symptoms and screening
Most family physicians are well aware of the symptoms of colorectal cancer. Right-sided colon cancer presents insidiously with anaemia symptoms, left-sided colon cancer present with change in bowel habit, alternating constipation and diarrhoea, passage of stale blood, and rectal cancers present with a feeling of incomplete emptying of the bowers. Occasionally, patients with colorectal cancer may also present with non-specific symptoms such as abdominal discomfort, bloating, pain, or even increased passage of flatus.
In fact, the best time to prevent or to cure colorectal cancer is when there are no symptoms. Most polyps and small colorectal cancers do not cause symptoms. This is because these lesions are small relative to the size of the lumen of the colon, especially on the right side of the colon where the stools are more liquid and can
go pass the lesion without causing any problems.
Stool occult blood test has been used for mass population screening. The newer tests (FIT or faecal immunochemical testing) use antibodies to detect the human globin component in blood, hence gives fewer false positive results. This compares favourably with the older guaiac-based test which detects haem in the stools and which may require dietary restrictions for up to 3 days prior to testing to ensure that the test is accurate. Sensitivity and specificity for these stools tests varies from 70% to 90%.
For more accurate testing, the colon can be evaluated by colonoscopy, barium enema or CT colonography (also known as virtual colonoscopy). All these require bowel prep for an optimal examination. Though some believe that colonoscopy is invasive and have a risk of perforation, people tend to forget that the radiological investigations also carry a risk (albeit a slightly lower risk) of perforation due to the fact that air has to be used to distend the colon. Colonoscopy also offers the advantage of sedation, removal of polyps and tissue for biopsies, and that it can easily distinguish any lesions from adherent stools.
It is well-accepted that most colorectal cancers follow the adenoma-carcinoma pathway of carcinogenesis, and as such, nipping any adenomatous polyps in the bud is tantamount to treating a future colorectal cancer. Cancers detected at screening also tend to be of earlier stage and have a better 5-year survival. 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 detection of polyps and early cancers. The recent trend of a plateau and a slight decrease in the incidence of colorectal cancer may be due to more colonoscopy screening and removal of polyps.
Surgery remains the main approach to treat colorectal cancer
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 one 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 for adjuvant therapy 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 in a palliative setting to control the cancer. Compared with the stress of surgery and/or chemotherapy and radiotherapy, regular colonoscopy screening is a much simpler process and can prevent colorectal cancer from occurring.
Article contributed by Dr Ho Kok Sun, General Surgeon, Mount Elizabeth Hospital. Dr Ho specialises in treating colorectal illnesses and has a strong interest in minimally invasive colorectal surgery.
This article was first published in Medical Grapevine.
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