Surgery for Colon Cancer

Surgeries can be categorised into curative, palliative, bypass, faecal diversion, or open-and-close.

Curative surgical treatment can be offered if the tumour is localized.

Very early cancer that develops within a polyp can often be cured by removing the polyp (i.e. polypectomy) at the time of colonoscopy.

In colon cancer, a more advanced tumour typically requires surgical removal of the section of colon containing the tumour with sufficient margins, and resection of mesentery (fatty lining of bowel containing lymph nodes) to reduce local recurrence (i.e. (hemi)colectomy).

If possible, the remaining parts of colon are joined together to create a functioning colon. In cases when anastomosis is not possible, a stoma (artificial orifice) is created. Usually these stomas are temporary to allow the bowel to heal up properly before the ends are joined back together. Tumours lower down in the bowel (rectum) have a poorer blood supply and take longer to heal, so a temporary stoma is often needed for these. If the tumour is very low down and the whole anal canal needs to be removed then a permanent stoma is necessary.

Curative surgery on rectal cancer includes total mesorectal excision (low anterior resection) or abdominoperineal resection.

In case of multiple metastases, palliative (non curative) resection of the primary tumour is still offered in order to reduce further symptoms caused by tumour bleeding and invading. Surgical removal of isolated liver metastases is, however, common and may be curative in selected patients; improved chemotherapy has increased the number of patients who are offered surgical removal of isolated liver metastases. Removal of lung metastases is also now possible.

If the tumour invaded into adjacent vital structures (T4) which makes excision technically difficult, the surgeons may prefer to bypass the tumour (ileotransverse bypass) or to do a proximal faecal diversion through a stoma.

The worst case would be an open-and-close surgery, when surgeons find the tumour unresectable and the small bowel involved; any more procedures would do more harm than good to the patient. This is uncommon with the advent of laparoscopy and better radiological imaging. Most of these cases formerly subjected to “open and close” procedures are now diagnosed in advance and surgery avoided.

Laparoscopic (keyhole) surgery is a minimally invasive technique that can reduce the size of the incision and may reduce post-operative pain. It is increasingly used for bowel resections.

As with any surgical procedure, colorectal surgery may result in complications including

• wound infection, Dehiscence (bursting open of wound) or hernia
• anastomosis breakdown, leading to abscess or fistula formation, and/or peritonitis
• Adhesions resulting in bowel obstruction
• Adjacent organ injury; most commonly to the small intestine, ureters, spleen, or bladder
• Cardiorespiratory complications such as heart attack (rare), pneumonia, blood clots.

Treatment of liver metastases

Around 25% of patients present with metastatic (stage IV) colorectal cancer at the time of diagnosis, and up to 25% of this group will have isolated liver metastasis that is potentially resectable. Lesions which undergo curative resection have demonstrated 5-year survival outcomes now exceeding 50%

Resectability of a liver metastasis is determined using preoperative imaging studies (CT or MRI), intraoperative ultrasound, and by direct palpation and visualization during resection. Lesions confined to the right lobe are amenable to en bloc removal with a right hepatectomy (liver resection) surgery. Smaller lesions of the central or left liver lobe may sometimes be resected in anatomic “segments”, while large lesions of left hepatic lobe are resected by a procedure called hepatic trisegmentectomy. Treatment of lesions by smaller, non-anatomic “wedge” resections is associated with higher recurrence rates. Some lesions which are not initially amenable to surgical resection may become candidates if they have significant responses to preoperative chemotherapy regimens. Lesions which are not amenable to surgical resection for cure can be treated with modalities including radio-frequency ablation (RFA), cryoablation, and chemoembolization.

More recently CyberKnife radiosurgery has been developed as a minimally invasive way of destroying liver metastases whilst avoiding major surgery, and can also be used to treat ‘surgically inoperable’ metastases close to major blood vessels etc.

Patients with colon cancer and metastatic disease to the liver may be treated in either a single surgery or in staged surgeries (with the colon tumour traditionally removed first) depending upon the fitness of the patient for prolonged surgery, the difficulty expected with the procedure with either the colon or liver resection, and the comfort of the surgery performing potentially complex hepatic surgery.

Types of surgery for Rectal Cancers

The surgical procedure recommended depends upon the extent of tumour involvement and the location of the cancer. For example, some rectal cancers are very small and limited to the surface of the rectal lining. Other cancers have grown through the entire rectal wall and are adherent (stuck) to nearby structures and organs, such as the abdominal or pelvic wall, the sacrum, the bladder, or the prostate gland. The extent of surgery needed to remove these two tumour extremes is very different.

In general, there are four types of operation:

• Transanal excision
• Low anterior resection (LAR)
• Abdominoperineal resection (APR)
• Pelvic exenteration

Most rectal cancers require an open surgical procedure, meaning that an incision is made through the abdominal wall to gain access to the lower intestine. This incision allows the surgeon to remove the tumour and examine the surrounding tissues. However, some early tumours can be removed endoscopically (through a telescope up the bowel) without an abdominal incision in a procedure called transanal excision.

A laparoscopic (keyhole) approach is often used in the treatment of colon cancer. Laparoscopy uses instruments inserted through several small incisions in the skin rather than a single large incision. Laparoscopic surgery is as safe and effective as open surgery for treatment of colon cancer.

In the case of rectal cancer, laparoscopic surgery may have an increased risk of cancer recurrence or sexual and/or bladder problems, compared to open surgery. However techniques are improving every year, and laparoscopic (keyhole) surgery is increasingly used in rectal cancer as well.

Transanal excision

The simplest type of surgery for rectal cancer is done without an abdominal incision by inserting instruments though the anal opening. This method can be used to remove large polyps or tumours that are small and located relatively close to the anus. However, newer techniques such as TEM (transanal endoscopic microsurgery) now permit excision of small tumours through the anus that are located higher up in the rectum.

Rectal tumours that can be successfully treated through a transanal excision are usually stage I, and have a favourable appearance when they are examined under the microscope. A “favourable appearance” means that the tumour tissue is forming or beginning to form normal gland structures. The medical term for this is “well differentiated” or “moderately differentiated” cancers (grade 1 or 2). “Poorly differentiated” grade 3 cancers have lost the ability to form normal gland structures, and these tumours tend to be more aggressive.

Superficial rectal cancers (T1) are the most suitable for transanal excision, although selected patients with T2 tumours may be eligible for this approach as well.

When a rectal tumour is removed through a transanal excision, the tissue will be analyzed under the microscope to determine if further surgery is needed. This examination also determines if postoperative (adjuvant) therapy is needed; postoperative therapy usually includes a combination of radiation therapy and chemotherapy. Radiotherapy, especially, is often recommended after a transanal excision, as the recurrence rates are significantly higher than with standard ‘open’ surgery even though they are small tumours.

Low anterior resection

A low anterior resection (LAR) is used whenever possible to preserve the rectum and anus, which allows the patient to have bowel movements in a normal fashion. However, the tumour must be located high enough in the rectum for this procedure to be recommended. The surgeon makes an abdominal incision to remove the cancerous tissue and then connects the remaining colon to the lower rectum, or in some cases, the upper anus.

Sometimes, the small intestine or colon is temporarily brought out to the skin of the abdominal wall, allowing passage of the stool into an external bag. This is called a temporary ileostomy or colostomy, which is necessary to allow the connected tissues to heal, as the rectum often has a poor blood supply. After a few weeks or months (depending on whether you have further chemotherapy treatment), the ileostomy or colostomy is closed and an external bag is no longer needed to collect the stool. The patient is then able to have bowel movements in a normal fashion (through the anus).

During the LAR procedure, the surgeon also removes all the lymph nodes (also called lymph glands) associated with the rectum. This is necessary because cancer cells have the ability to travel through the body using the lymphatic system. Lymph nodes contain special cells that trap cancer cells; removing the lymph nodes helps to ensure that cancer cells are not able to spread beyond the lymph nodes. The tissue removed from the lymph nodes is examined to determine if further treatment will be needed after surgery.

Abdominoperineal resection

An abdominoperineal resection (APR) is used when tumours cannot be completely removed using LAR, most commonly because the tumour is too low down and close to the anus. APR requires an abdominal incision as well as an incision to remove the anus. This results in the need for a permanent colostomy.

During an APR, the lymph nodes in the vicinity of the rectum are removed, just as in the LAR.

Pelvic exenteration

If a cancer has invaded nearby organs, a more extensive operation may be needed. In this situation, it is often possible for the surgeon to remove a part of certain organs such as the bladder or prostate or a bit of the sacrum (tailbone). If the function of these organs cannot be saved because of the extent of tumour involvement, the entire organ may need to be removed.

Rarely, all of the tissues and organs within the pelvis (including the bladder, prostate [in men], and/or uterus [in women]) must be removed to successfully treat the cancer. This is a major operation called pelvic exenteration.

Most patients undergoing pelvic exenteration require a permanent colostomy. If the bladder is removed, the patient may also need a urostomy, an artificial opening on the front of the abdomen that allows urine to leave the body. Pelvic exenteration can cause a number of complications and may not cure a person due to the widespread nature of the cancer.

For many patients with locally advanced rectal cancer, an alternative to pelvic exenteration is the administration of chemotherapy and radiation therapy before surgery. This can often shrink the tumour, allowing the surgeon to perform an LAR, an APR, or a more extensive operation, depending on how much cancer remains after chemotherapy and radiation therapy.

BOWEL FUNCTION AND SEXUAL FUNCTION AFTER SURGERY

Bowel function following rectal cancer surgery depends upon the specific operation that was performed and whether radiation therapy was also used. Following a LAR, many patients experience initial difficulty with bowel control even if the anal sphincter (the valve that controls elimination of stool) has been preserved. You may feel a sense of bowel urgency and need to pass stool more frequently. For most patients, bowel function improves over time (even up to two years), although it may not return to presurgery levels. Having radiation therapy as well can increase the chance that bowel function may change permanently.

If the connection between the colon and the anus was made very close to the anal opening, there is very little “rectal reservoir,” or room, to store faecal matter before needing to move the bowels. These patients may have an increased frequency of bowel movements and some people have difficulty emptying the bowels. Sometimes, a larger reservoir can be created out of the colon (colonic J Pouch) prior to connecting it to the lower rectum or anus. This provides more space to store faecal matter and can allow the person to have better bowel function.

Sexual function can be altered following LAR, and APR. This is because the nerves that control sexual function run along the front of the tailbone, very close to the rectum, and can sometimes be damaged during surgery. The risk of sexual dysfunction can also increase if radiotherapy is given as well. This can happen in up to 50% cases. Often the problem is only ‘partial’ and can be resolved over time with treatment. Permanent complete impotence is relatively rare.

Life with a colostomy

Having a colostomy can alter a patient’s body image, which can be challenging, both physically and emotionally. However, with education and support, it is possible to lead an active life with a colostomy. A team effort, which includes the colorectal surgeon, oncologist, and a stoma nurse, is invaluable in counseling and educating the patient and their family before surgery, and also in the care and rehabilitation required after the procedure.