The colon and rectum are parts of the body’s digestive system and together form a long, muscular tube called the large intestine. The colon is the first 6 feet of the large intestine and the rectum is the last 8-10 inches. The last part of the rectum contains the rectal sphincter or anus. The rectal sphincter is the muscle that controls defecation. Preservation of the rectal sphincter during surgery for rectal cancer is necessary in order to maintain control of bowel function. Treatment approaches differ between cancers of the colon or rectum, and are therefore discussed separately. A separate section has been created for Colon Cancer.
Adenocarcinoma is the most common type of cancer that originates in the cells that line the rectum or large intestine. It accounts for over 90-95% of cancers originating in the rectum. Other types of cancer including carcinoid and leiomyosarcoma also originate in the rectum, but are not referred to as rectal cancer. This treatment overview deals only with adenocarcinoma of the rectum, which will be referred to as rectal cancer.
The treatment of rectal cancer may involve several physicians, including a gastroenterologist, a surgeon, a medical oncologist, a radiation oncologist, and/or other specialists. Care must be carefully coordinated between the various treating physicians involved in management of your cancer.
Stage I adenocarcinoma of the rectum is relatively uncommon and is usually curable by surgical removal of the cancer. Different types of surgery may be recommended depending on the location and specific characteristics of the cancer.
Low anterior or abdominoperineal resection: A low anterior resection (LAR) involves an incision across the abdomen and removal of the cancerous part of the rectum along with some surrounding tissue and lymph nodes. This is often done for cancers that are in the upper part of the rectum. Lower cancers may be treated with removal of the rectum along with extensive removal of surrounding tissues (total mesorectal excision). Depending on where the cancer was and how much of the rectum was removed, the colon may be reconnected to the remaining part of the rectum or to the anus. When possible, the surgery will allow a patient to continue to pass waste through the anus. Some patients, however, may require a temporary or permanent colostomy (an artificial opening that allows waste to pass from the colon to the outside of the body).
If the cancer is very low in the rectum (near the anus), a patient may need to have an abdominoperineal resection (APR). This involves an incision in the abdomen and an incision around the anus. Because both the rectum and the anus are removed, an APR requires a permanent colostomy.
Trans-anal resection or trans-anal endoscopic microsurgery: In some cases it may be possible to remove the cancer through the anus without making an incision in the abdomen. Techniques for removing the cancer in this way include trans-anal resection and trans-anal endoscopic microsurgery (TEM). The operations involve cutting through all layers of the rectum to remove invasive cancer as well as some surrounding normal rectal tissue. This procedure can be used to remove some Stage I rectal cancers that are relatively small and not too far from the anus. If the cancer is found to have certain high-risk features, more extensive surgery may be recommended. These local treatments of rectal cancer offer the advantage of quicker recovery after surgery, but may be linked with a higher risk of cancer recurrence than more extensive types of surgery.1
The progress that has been made in the treatment of rectal cancer has resulted from improved surgical techniques and the development of adjuvant treatments in patients with more advanced stages of cancer and participation in clinical trials. Future progress in the treatment of rectal cancer will result from continued participation in appropriate clinical trials.
Improvement in staging: A small fraction of patients with Stage I rectal cancer will relapse following surgery. This is thought to be due to inadequate staging with failure of ultrasound to detect nodal metastases. Other factors, such as how the cancer looks under the microscope, may also have an impact on survival. Patients with poorly differentiated tumors (tumors with more abnormal-looking cells), and those with vascular invasion may have an increased risk of relapse, especially after local trans-anal incision.2 Future studies may help better identify patients who need adjuvant therapy.
Improvements in surgery: Laparoscopic surgery is used for many types of surgery with the short-term advantages of less pain, fewer wound complications, quicker post-operative recovery, and shorter hospital stays. Instead of making one long incision in the abdomen, the surgeon makes several smaller incisions. Special long instruments are inserted through these incisions to remove part of the rectum and lymph nodes. One of the instruments has a small video camera on the end, which allows the surgeon to see inside the abdomen. Once the diseased part of the rectum has been freed, one of the incisions is made larger to allow for its removal.
Laparoscopic-assisted surgery appears to be about as likely to be curative as the standard approach for earlier-stage cancers.3 However, there is still limited information from randomized trials about the approach. In addition, laparoscopic surgery requires special expertise and patients need to be treated by a skilled surgeon who has done a lot of these operations.