Colon / Colorectal Cancer
Colon cancer refers to cancer that arises in the colon. This is in contrast to Rectal Cancer that arises in the rectum. Collectively, both of these cancers are known as Colorectal Cancer.
The colon, also known as the large intestine, consists of the ascending colon, transverse colon, descending colon, and sigmoid colon. Any cancer arising in these areas is known as colon cancer.
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How is Colon Cancer diagnosed?
Colon cancer is most commonly diagnosed during a colonoscopy. One group of patients will be undergoing colonoscopy due to suspicious symptoms while the other group will be undergoing screening colonoscopy with the absence of symptoms.
A colonoscopy will allow the detection of the cancerous growth in the colon. In addition, biopsies can be taken to allow a definitive diagnosis.
In a minority of patients, the discovery of a colonic growth is an incidental finding made on a scan performed for other reasons. The patient will then be advised to undergo a colonoscopy to confirm the diagnosis.
How is Colon Cancer treated?
The treatment of colon cancer consists of two components, namely Surgery and Chemotherapy and/or Radiotherapy.
Surgery is the first-line treatment for all colon cancers that have not spread. This means that the cancer is still contained within the colon and the lymph nodes in the vicinity of the colon.
Surgery for colon cancer involves removal of the segment of the cancerous colon and then joining (anastomosis) of the two ends of the colon. By doing so, the cancer is removed while the patient is able to pass motion (urinate) as per normal.
During the removal of the colon, the associated lymph nodes are also removed. This is important as there is a possibility of cancer spread to the lymph nodes and complete removal is essential in any colon surgery.
Colon surgery can be performed as a Keyhole (laparoscopic) or open surgery. In the current era, keyhole surgery is the first option offered to the patient. Open surgery is recommended for patients with unique circumstances such as prior open surgery on the abdomen, large and advanced colon tumour, and patients with heart and lung conditions.
Chemotherapy for colon cancer is usually started after surgery is completed and the cancerous colon has been removed. This occurs about 4-6 weeks after the surgery to allow the patient to recuperate and recover their strength.
Chemotherapy is not definite after colon surgery. The decision for chemotherapy rests on the characteristics of cancer which can only be determined after examination under a microscope (histology testing). Chemotherapy is recommended for colon cancers that have spread to the lymph nodes (node-positive disease), large and locally advanced cancers (T4 tumours), and for cancers that subsequently show spread to distant organs like the liver and lung.
In a minority of colon cancers, chemotherapy is started before surgery has taken place. This approach is for colon cancers that have shown spread to distant organs like the liver and lung or for locally advanced cancers that may benefit from some shrinkage from the chemotherapy prior to surgery.
How is Colon Cancer staged before surgery?
Upon establishing the diagnosis of colon cancer, staging needs to be carried out before any surgical option can be discussed.
Staging is essential in determining if any distant spread (metastases) of the cancer has occurred. In addition, the staging also allows the assessment of spread to the lymph nodes and to determine if the tumour is invading into other organs.
Staging is carried out with a CT (computed tomography) scan of the chest and abdomen. The CT scan is a highly accurate scan that allows visualisation of any spread, particularly to the liver and lungs which are the commonest sites for metastases. The CT allows visualisation of enlarged lymph nodes and this is critical for planning for the surgery. Lastly, the CT also allows assessment of tumour invasion into other organs and this is essential for operative planning and pre-operative counselling for the patient.
For rectal tumours, an additional MRI scan of the pelvis is an essential part of the staging process to determine the extent of invasion of the tumour and to aid in the decision making for pre-operative radiotherapy.
Colon cancer surgery can be performed either as a Keyhole (laparoscopic) or open surgery. Both methods employ the same principles of removal of the tumour and lymph nodes and Re-Establishment of the colon and faecal flow
Keyhole surgery is performed using designed-for-purpose keyhole instruments. These are instruments with long shafts and grasping jaws to take on the role of the surgeon’s hands when compared to open surgery. In addition, blood vessel-sealing energy devices and staplers are also used during the surgery.
Keyhole surgery is carried out through three to five small wounds (incisions) on the abdomen. These range in length from 5mm to 15mm. In addition, there is a separate incision of about 5cm in length that is required to retrieve the segment of the cancerous colon.
The execution of the surgery involves freeing up the targeted colonic segment from its original location. This is followed by isolation and sealing off of the major blood vessel supplying the tumour. The colonic segment containing the tumour is then cut off at both ends with a 5cm margin from the tumour. It is not possible to separate the tumour from the colon and hence the need to remove a portion of the colon.
With the removal of the colonic segment, there is a need to re-join up the two ends of the colon to allow the normal flow of faeces. The two cut ends of the colon are brought together and joined together using either specialized surgical staplers or stitching by hand.
The recovery process can be divided into two phases. The first phase is the Hospitalisation stay which is usually between 3-10 days and the second phase is the Recuperation phase which can stretch to the next 1-3 months.
During the hospitalisation stay, resumption of a normal diet will take place over a period of 3-4 days. The usual practice is for a period of abstinence of food and drinks for about 1-2 days after which diet is gradually introduced. However, some surgeons practice the ERAS protocol (Enhanced Recovery After Surgery) which prioritises early dietary resumption as one of the key tenets. For patients on the ERAS protocol, fluids can be resumed as early as the evening of the surgery.
Some patients will have a surgical drain leading out from the abdomen. This is a small plastic tube that will stay for a few days to allow the fluid in the abdomen to be drained out. In addition, for patients who underwent prolonged or complex surgery, a nasogastric tube that leads out from the nostril may be needed to allow gastric fluid to drain out. All patients should expect to have an intravenous cannula in the first few days to allow the administration of fluids and medications.
Most patients can expect a hospitalisation stay for about an average of 4-5 days after which they will be discharged to recuperate at home.
During the home recuperation phase, it is expected that the initial bowel movements may still fluctuate before settling down to a regular pattern. The bowel pattern that is established at 6 months after surgery will usually be permanent. The surgical wounds will usually heal after 2 weeks and bathing can usually be done as early as the day after surgery. It is expected that the patient will feel a little weaker after the surgery. Most patients will feel that they are close to their pre-surgery energy levels about 1-2 months after the surgery.
Emergency surgery for colon cancer is usually performed for tumour perforation or tumour obstruction.
In the case of perforation, it can occur due to the tumour eroding through the colon or the colon tearing due to tumour obstruction. In both situations, emergency surgery will be needed due to the presence of faeces and pus in the abdomen. The surgery will also certainly be open surgery and there is a high likelihood of having to create a stoma.
In the case of obstruction, this is due to the excessive growth of the tumour resulting in the hold-up of faeces and hence obstructing the colon. There are two options available for the treatment of obstruction. The first option is for immediate emergency surgery which is almost certainly performed as open surgery.
The second option will be for stenting of the colon if the location of the tumour is suitable. Stenting involves putting in a metallic ‘scaffolding’ that will expand and push apart the tumour and hence allowing faeces to flow through. Stenting will help to avert emergency surgery and allow the definitive surgery to be performed in 1-2 weeks with the possibility of keyhole surgery.
A stoma is formed by bringing up a segment of either the small or large intestine to the skin surface. This allows the faeces to be diverted away into a bag attached to the skin instead of flowing down and causing more damage.
Stomas are usually created only as a last resort if the intestinal ends cannot be joined (anastomosed) back. This usually occurs in the case of an emergency such as tumour obstruction or perforation. Occasionally, stomas are also created in the non-emergency setting to prevent obstruction. Stomas can be reversed, and the intestines joined back in the future.
Caring for and managing the stoma can be done by the patient himself. Adequate care and training will be provided to the patient and their family members during the hospitalisation period. The stoma bag is designed to avoid being torn and is also sealed off so that there is no feculent smell associated with it.
Colon cancer is a very treatable cancer. The mainstay of treatment is the surgical removal of the tumour with the colonic ends joined back. Chemotherapy may be needed after the surgery, depending on the stage of the tumour. A CT scan is needed before the surgery to determine if the tumour has spread and also to allow planning for surgery. A stoma is usually only needed for emergencies such as tumour perforation or obstruction.