Rectal Cancer: The Basics

How is rectal cancer diagnosed and staged?

Once rectal cancer is found by the screening tests, further tests are needed to determine the extent of the tumor. The tests used to determine spread of the tumor are CT scans, MRIs, and endoscopic ultrasound (EUS). The EUS is a type of ultrasound that uses sound waves to determine the depth of the tumor and whether or not surrounding lymph nodes are involved. A biopsy is typically done during an EUS, colonoscopy or proctoscopy (a test which allows the doctor to view only the rectal area) to verify the type of tumor. Carcinoembryonic antigen (CEA ) level is a marker for colon cancer that is found in the blood and which is elevated in 95% of cases. With these tests, a stage is determined to help dictate the necessary treatment. The stages are:

Stage 0: the tumor is confined to the first layer of the rectal tissue. It is also called carcinoma in situ
Stage I: the tumor has spread through the innermost lining of the rectum into the second and third layers of the inside wall of the rectum, but has not spread outside the rectum
Stage II: the tumor has spread through the rectal wall into surrounding tissue, but has not spread to the lymph nodes
Stage III: the tumor has spread to the surrounding lymph nodes, but has not spread to other areas of the body
Stage IV: the tumor has spread to other areas of the body, such as the liver and lungs

There are other staging systems used in clinical practice, but this one is the most commonly used. See Understanding Your Pathology Report for more information.

What are the treatments for rectal cancer?

Surgery

Over the past twenty years, there have been significant improvements in surgical techniques for the treatment of rectal cancer. In the past, a majority of patients required a colostomy after rectal cancer surgery and developed significant side effects (such as incontinence and male impotence) from nerve damage that frequently occurred during the surgery. The utilization of pre-operative chemoradiation (combination of chemotherapy and radiation) and improved surgical techniques has led to fewer side effects and fewer patients requiring colostomy.

Surgery is the most common treatment for rectal cancers. If the tumor is relatively small, it can be removed by a surgical procedure called local excision, which removes only the cancerous area.

A larger tumor requires a resection (removal of the tumor and some healthy tissue surrounding it) and anastomosis (the two tumor-free ends of the bowel are reconnected). If the bowel ends cannot be reconnected, a colostomy is made. Preoperative chemotherapy & radiation (called neoadjuvant therapy) can improve how successful the surgeon is at completely removing the tumor.

The most commonly performed surgical procedure today is the total mesorectal excision or TME. This procedure removes the rectum and the mesorectum, an area of fatty tissue below the rectum that contains lymph nodes, which are the most common area for the cancer to spread. In the hands of an experienced surgeon, the number of patients requiring colostomy with this procedure is low. TME, along with neoadjuvant chemoradiation, has led to decreases in recurrences in the rectal area from 40% to less than 10% and has improved overall survival from 50 to 75% in the last 40 years.

Diagram of TME excision

In addition, surgeons used to perform the resection through the abdomen (called abdomino-perineal resection or APR). Today, the TME is most often performed with a low anterior resection (LAR), which

In some cases, even though the surgeon is able to remove all of the visible tumor, a person may also be recommended chemotherapy and/or radiation therapy to prevent the cancer from coming back (also called recurrence). These recommendations are based on what the pathologist finds when examining the tumor under a microscope, including if the margins of the specimen are free of tumor, the tumor size, and if any blood vessels or lymph nodes are involved.

The normal rectum acts as a holding area for stool. When an ultra low rectal resection and anastomosis are needed, the holding area is lost, leading to more frequent bowel movements and/or incontinence. To alleviate this problem, the colonic J-pouch was developed. This procedure uses the remaining bowel to create a J-shaped pouch, which then acts as a new holding area for the stool. It is usually about 5-6 cm in length and significantly reduces the number of bowel movements and incontinence.

Radiation and Chemotherapy

Patients with stage 0 and I disease are typically treated with surgery only. Patients with stage II and III disease are at a high risk of recurrence and should be treated with chemotherapy and radiation either pre-operatively (called neoadjuvant therapy) alone or in conjunction with post-operative therapy (called adjuvant therapy).

Due to the large size of the pelvis (the bony structure in which the rectum lies), it is often difficult for a surgeon to remove enough normal surrounding tissue to obtain adequate tumor-free margins. This is especially true for larger tumors. Giving chemoradiation pre-operatively can shrink a tumor that would not have been surgically removable initially, therefore making these patients candidates for potentially curative surgery. This is known as "downstaging" the tumor. Downstaging with chemoradiation has also allowed patients with tumors that would otherwise require a colostomy to now have a resection and anastomosis following treatment. Studies have shown that giving fluorouracil (5-FU) in combination with radiation therapy (called chemoradiation) before surgery (called neoadjuvant therapy) results in less short and long term toxicity and fewer recurrences of the tumor in the rectal area, when compared to giving the therapy after surgery. Because of this, neoadjuvant therapy has become the standard of care for rectal cancer.

Patients with stage IV rectal cancer may be offered resection of the tumor, radiation and/or chemotherapy. Some patients may be candidates for surgical management of cancer that has spread to other nearby organs (i.e. liver, ovaries). Most of these treatments are to alleviate symptoms, but are not considered curable.

Therapy for patients with advanced disease includes a combination of fluorouracil, leucovorin, and irinotecan (CPT-11 or Camptosar) or oxaliplatin (Eloxitin). Regimens incorporating irinotecan or oxaliplatin were found to be more effective than fluorouracil and leucovorin alone in these patients.

Bevacizumab (Avastin) is a type of treatment called anti-angiogenic therapy. Tumors need nutrients to survive and are able to get these nutrients by growing new blood vessels. This medication works by attacking the new blood vessels the tumor has formed -- in other words, by cutting off its food source. Bevacizumab is used in combination with chemotherapy.

Cetuximab (Erbitux) and panitumumab (Vectibix) are types of monoclonal antibodies that target cancer cells specifically, sparing the normal cells and therefore causing fewer side effects. Cetuximab causes the patient's immune system to recognize the cancer cells as foreign and attack them and is given either alone or in conjunction with chemotherapy agents.

Epidermal growth factor receptor (EGFR) is abnormally over expressed in many cancers (including those of the colon and rectum), so inhibition of EGFR can result in a decrease in tumor cell growth and decreased production of other factors responsible for metastasis (tumor spread). Panitumumab exerts its cancer fighting properties by competitively inhibiting the binding of epidermal growth factor to EGFR, which prevents epidermal growth factor from working and hence not allowing cancer growth to occur.

Capecitabine (Xeloda), an oral form of fluorouracil, is also being used in the treatment of rectal cancers when the patient cannot tolerate the above therapies or has progressed on these therapies.

Follow-up care

Once a patient has completed chemotherapy, he or she must be followed closely for recurrence. The guidelines for follow-up surveillance, written by the National Comprehensive Cancer Network, are: physical exam (including digital rectal exam) every 3 months for 2 years, then every 6 months for 3 years; CEA level checked (if elevated at diagnosis) every 3 months for 2 years, then every 6 months for 3 years; and colonoscopy in 1 year, with a repeat in 1 year if abnormal, or every 2-3 years if no polyps are found. There is not enough evidence to support or refute the use of chest x-ray or CT scan for surveillance at this time, so this varies from physician to physician and is more likely used in higher risk cases.

Clinical trials have played and continue to play an important role in the treatment of colorectal cancer. In the past 20 years, considerable improvements have been made in colorectal cancer therapy, with overall survival rates increasing from 45 to 75 percent. The treatments we have today were refined through clinical trials, and many new avenues continue to be explored. Talk with your physician about current clinical trials for rectal cancer available in your area.

This article is meant to give you a better understanding of rectal cancer. Use this knowledge when meeting with your physician, making treatment decisions, and continuing your search for information.

You can also learn more about colorectal cancer on OncoLink through the related links on the left.

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How is rectal cancer diagnosed and staged?

What are the treatments for rectal cancer?

Surgery

Radiation and Chemotherapy

Follow-up care