Colorectal cancer: More detectable, more treatable
Consultant Colorectal Surgeon Dr Ho Kok Sun discusses the latest in screening and treatment options for colorectal cancer – a very preventable and treatable disease.
Colorectal cancer is the most common cancer among men and the second most common cancer among women in Singapore. And it is not only common, it is a serious disease. It is the second most common cause of mortality in men and the third most common cause of mortality in women.
Fortunately, improvements in screening techniques and surgical procedures have increased the likelihood of catching the cancer, and treating it effectively.
New screening techniques
The main non-invasive test for colon cancer involves testing for blood in the stool. Up to 20 years ago, the standard stool guaiac test was used to detect hidden (occult) blood in stools.
However, those tests were not able to differentiate human blood from other types of blood and thus, people had to abstain from meat for three days before taking the test. The sensitivity of the guaiac-based test was only 10-30 per cent but it increases if three separate samples are taken over three consecutive days.
Today, there is the faecal immunochemical test (FIT) that detects human blood from the lower intestines. It is very sensitive and can detect up to 0.3 ml of blood in the colon. This test is also able to distinguish human blood from other types of blood which means that patients do not have to be vegetarian before the test.
A third test involves detecting Tumour M2-PK, an enzyme found in cancer cells. It does not depend on detecting blood in the stool and is reputed to be able to detect 80 per cent of cancers and 40 per cent of polyps. However, this test is not available in Singapore and is more commonly used in Indonesia and Malaysia. It is still unclear if this test is useful and more data is needed.
Apart from non-invasive tests for colon cancer, there are also more invasive tests as well, such as barium enemas, CT colonography and colonoscopies.
All three tests require bowel preparation, which makes it more inconvenient for patients. In addition, these tests also have a perforation risk. The risk is one in 1,000 in colonoscopy, one in 2,000 for CT colonography and one in 400-4,000 for barium enemas.
In terms of accuracy, colonoscopy is treated as the gold standard, followed by CT colonography and barium enemas.
Once a tumour is discovered, surgery is needed to remove it. Over the years, surgical procedures have also improved. About 20 or 30 years ago, there was only one solution: open surgery. However, this has evolved into smaller and smaller incisions and today, surgeons are now able to use laparoscopic surgery to minimise the size of the incisions needed. Smaller incisions mean less pain, faster healing and a lower chance of infection.
Laparoscopic surgery now comes in different options: standard, robotic and single-access port. The standard laparoscopic surgery involves putting a camera through the navel, and having three to four ports, 5-12 mm in size, for instruments and to remove the tumour.
Single incision port surgery means a single incision is used with all the instruments going through the same port. More advanced curved instruments are used for this procedure.
Robotic surgery is the latest in laparoscopic surgery, where robotic arms are used to do the surgery. Relying on robotic arms reduces fatigue for surgeons and enables greater precision. This technique also offers greater magnification (up to 10 times, compared to three times for laparoscopic surgery). As a result, it allows for very accurate dissection that preserves all the nerves.
Laparoscopic surgery has also been assisted by the development of colonic stenting. This is a procedure to handle intestinal obstruction that converts emergency surgery to elective surgery.
Because of the tumour, some patients would be admitted to hospital bloated and vomiting because their blocked intestines caused their stools to back up. This was previously an emergency situation and thus ruled out laparoscopic surgery.
With colonic stenting, a stent, which looks like a wire mesh, is inserted to open up the intestines. It allows distended bowels to decompress and to allow the stools to come out naturally. Patients can return home, rest and build up their strength over the next week so that laparoscopic surgery can be performed on them later.
Other types of minimally invasive surgery
Apart from laparoscopic surgery, other forms of minimally invasive surgery can be used, depending on the location of the tumour. Endoscopic surgery is where the surgery is done through the colon; there is no cut on the stomach. This is good for large polyps but it is still not clear if it is feasible for early stage cancers.
For very low rectal cancers, trans-anal surgery exists as an option. This procedure makes low cancers easier to reach but it comes with safety issues because if the stitch to close up the rectum gives way, it exposes the tumour cells to the cut.
Finally, there is a more experimental procedure known as NOTES, which stands for natural orifice trans-luminal endoscopic surgery. With NOTES, there is no incision on the skin. Instead, the instruments enter through natural orifices and then cuts are made via the stomach, colon or vagina. This surgical procedure is much harder than conventional laparoscopic surgery because the surgical tools are still not quite suitable.
Healing is also complicated with NOTES because potential infections are much more dangerous than if there is infection from laparoscopic surgery. A skin incision could lead to a wound infection, while a problem with muscle healing, could lead to a hernia. However, if you have a problem with the colon, you could get peritonitis, which is a medical emergency.
Advances in screening for colorectal cancer mean that it is now possible to catch this deadly form of cancer earlier than before. In addition, advances in minimally invasive surgery mean that patients who undergo this type of procedure experience less pain, shorter hospital stay, less infection and better outcomes overall.
Written by Jimmy Yap
Tags: cancer diagnosis, cancer laparoscopic (minimally invasive) surgery, cancerous polyps, colonoscopy, colorectal cancer, common cancer, gastrointestinal cancer, robotic surgery