Please see the section on colon cancer first, which contains information relevant to rectal cancer. Then come back to this section.
The rectum is the section of the lower gastrointestinal system that connects the colon to the anus, where waste matter passes out of the body. Like the colon, the rectum is part of the large intestine, and rectal and colon cancers are often referred to together as colorectal cancers. While the two conditions are part of the same disease process, the treatment of rectal cancer is different from colon cancer because of its unique anatomic location.
Like colon cancer, rectal cancer develops slowly over a period of years. Most cancers begin within a polyp, also called an adenoma. These are small growths of non-cancerous tissue that protrude from the lining of the large intestine. Over time, as these polyps grow, they can become cancerous and begin to invade the layers of tissue that form the wall of the rectum.
RECTAL CANCER STAGING
Treatment and prognosis (outcome) of rectal cancer depend upon the stage of the cancer. Staging of rectal cancer is based upon how far the cancer has penetrated into the wall of the rectum, whether the cancer has spread to lymph nodes located around the rectum, and whether the cancer has spread via the bloodstream to other organs (called metastatic spread).
The initial evaluation of a rectal cancer usually involves a colonoscopy. Chest, abdominal and pelvic CT scans are often recommended to look for evidence of cancer spread within the abdominal cavity and/or lungs. Other tests include a specialized rectal ultrasound or magnetic resonance imaging (MRI) scan.
The final stage of a rectal cancer is confirmed by the findings during surgery, which is the most accurate way to determine how far the tumour has spread.
There are two staging systems for rectal cancers:
- The TNM system (tumour, nodes, metastases) is most commonly used (see colon page)
- Less frequently, a modification of the Dukes system is used (see colon page)
RECTAL CANCER TREATMENT
The majority of rectal cancers are treated with a combination of surgery, radiation, and chemotherapy.
- Stage I rectal cancer (Dukes A, T1/2 N0 M0) — Surgery alone may be curative. Short course radiation therapy is sometimes given for very low T2N0 cancers.
- Stage II or III (Dukes B/C – T3/4 N0/1/2 M0) — Chemotherapy and/or radiation therapy are typically recommended before surgery (referred to as neoadjuvant therapy). Chemotherapy is often also used after surgery (adjuvant therapy)
- Stage IV (M1, distant spread) — Predominantly treated with chemotherapy, with or without surgery and radiation therapy, depending on the individual situation.
Types of surgery
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.
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.
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.
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.
CHEMOTHERAPY AND RADIATION
Chemotherapy and radiation therapy are recommended in addition to surgery for most patients with stage II or III rectal cancer. These treatments improve the likelihood of surviving cancer. Even when all visible signs of cancer have been removed by the surgeon, between 20 and 50 percent of patients will have a recurrence of their cancer if it is treated with surgery alone.
One reason for this relatively high recurrence rate is that the area of the pelvis where the rectum is located is a “tight space” , a bit like a narrowing funnel, and it is sometimes difficult for the surgeon to remove a sufficient amount of tissue around the tumour; this means that all of the cancer cells in the surrounding tissue may not be removed. In addition, tiny cancer cells may have escaped from the lymph nodes and spread to other organs. The combination of chemotherapy and radiation helps to reduce the chance of recurrence by targeting any remaining cancer cells.
There are two ways to administer (chemotherapy) and radiation in patients who have rectal cancer:
Preoperative chemotherapy and radiation
Neoadjuvant or induction chemoradiotherapy is done before surgery in an attempt to shrink the tumour before it is removed. This approach is usually recommended if the tumour is stage T3 or T4 of if there are involved lymph nodes on the scan, because, in this situation, neoadjuvant chemoradiotherapy has the following benefits:
- 1. Reduces the risk of local recurrence and increases survival
- 2. Has fewer short term and long-term side effects (compared to postoperative chemoradiotherapy)
- 3. Provides a better chance of avoiding a permanent colostomy.
Other patients may benefit from preoperative chemoradiotherapy, including the following:
- Patients whose tumours are located low in the rectum and an abdominoperineal resection (APR) will likely be needed. A major goal of preoperative therapy in this circumstance is to try to preserve the anal sphincter and avoid a permanent colostomy.
- If the tumour is less advanced (ie, T1 or 2) but there are positive lymph nodes. If the initial staging studies suggest that surgery might not successfully remove all of the tumour
- When surgery is performed first, chemoradiotherapy would only be needed after surgery if lymph nodes are involved or the tumour has grown through the entire bowel wall. Studies have shown that giving radiation before surgery works better than giving it after surgery. If there is any doubt on the preoperative scans, the oncologist will likely recommend having preoperative radiotherapy. I tend to do this as I believe that if there is any doubt it is better to potentially overtreat a cancer than to potentially undertreat it, as the consequences of undertreating can be disastrous later on.
So, choosing to have chemoradiotherapy before surgery may commit the patient to more treatment than they would have needed if surgery had been performed first. This is a difficult decision that should be shared between the patient and the physician.
Chemoradiotherapy usually works very well, with responses seen 80 – 85% of the time.
There may be clinical trials running of new ways of treating rectal cancers with more intensive chemotherapy and radiotherapy to improve survival rates. In addition I am running a study of using additional ‘special’ functional MRI scans before, during, and after radiotherapy. The aim of this study is to look at blood flow within the cancer, and to see if it is possible to predict response to chemotherapy and radiotherapy much earlier. This is important as if the radiotherapy is not working it would be important to proceed to surgery as soon as possible. If appropriate your oncologist will mention these studies.
The use of chemotherapy in addition to radiation therapy is critical to the success of neoadjuvant therapy. Previously, the most common way to give chemotherapy and radiation before surgery was to give continuous intravenous 5-FU with an infusion pump that was used throughout the 5 or 6 weeks of treatment.
These days an increasingly popular alternative is to give a daily dose of oral Capecitabine (Xeloda®) during radiation therapy, largely because it is more convenient for the patient. Studies suggest that the effectiveness of Capecitabine is equivalent to that of 5FU.
Patients who undergo neoadjuvant chemotherapy and radiation therapy often receive an additional six months of chemotherapy alone after surgery. There are several reasonable options, including:
- Oral therapy with Xeloda® (Capecitabine)
- Use of two drugs, Oxaliplatin and 5-FU or Capecitabine (this regimen is called FOLFOX or CAPOX)
Both radiation and chemotherapy can cause side effects, particularly when used together.
Chemotherapy - See also section on individual drugs
The most common side effects with 5FU or Capecitabine are diarrhoea, mucositis (soreness in the mouth), hand and foot syndrome, which causes soreness, redness and peeling of the skin of the palms and soles of the feet. Supplemental vitamin B6 (also called pyridoxine) may provide benefit in this situation. All chemotherapy drugs can potentially affect the blood counts and increase the chance of picking up infection, and you should consult a doctor immediately if you feel unwell.
Most patients tolerate chemotherapy reasonably well and many are able to continue working during treatment, often with a reduced schedule of hours due to fatigue. Hair loss is an uncommon side effect of the chemotherapy drugs used for rectal cancer.
Combined chemotherapy and radiation
Possible side effects of 5-FU / Capecitabine and radiation include fatigue, diarrhoea, irritation or inflammation of intestinal tissue leading to a sense of bowel urgency, bleeding and discomfort in passing stool, and skin irritation around the anus.
FOLLOW-UP AFTER TREATMENT
See Colon cancer section. For rectal cancer, an additional CT scan is often performed 6 months after completion of treatment.
OPTIONS FOR RECURRENT CANCER
If a rectal cancer recurs in the area of the rectum, the best therapy depends upon several factors, including what treatments were used previously and where the new cancer is located.
If no previous radiation has been administered, this can be used in combination with surgery.
If previous radiation has been given it may still be possible to remove the recurrent cancer surgically, although the risks of complications is higher following previous radiotherapy as scar tissue can form in the pelvis, making the surgery more technically challenging. If the recurrence has invaded other adjacent structures, a pelvic exenteration may be needed.
A recent development has been the new CyberKnife robotic radiosurgery system. This is a very accurate form of highly focussed radiotherapy that can be given for local recurrences and may enable the patient to avoid major surgery such as an exenteration. It can be given to patients who have had radiation before. Early data indicates that the results are similar to surgery in this instance. Please ask your oncologist for further information and see the CyberKnife section of this website.
The treatment of patients with advanced or metastatic rectal cancer depends upon the extent and location of tumour involvement. Although the majority of patients cannot be cured by any therapy, some patients with limited involvement may be cured by further surgery and/or chemotherapy.