Colorectal Cancer Section
Colon and rectal cancer is the 2nd or 3rd most common cause of cancer-related death in the United States and in Canada. In the U.S. about 150,000 new cases are diagnosed each year. The colon and rectum are the 2 parts of the large intestine (also known as [aka] the large bowel). The rectum is the last 5 inches of the large bowel that leads to the anus. The colon is about 3 to 4 feet in length and runs from the small intestine to the rectum. The vast majority of colorectal cancers start as benign polyps that develop from the inner lining of the large bowel that is called the mucosa. Although the exact time varies from patient to patient it is thought that it takes, on average, about 5 to 7 years for a polyp to develop into an invasive cancer. Periodic colonoscopy examinations are advised in order to detect and destroy benign polyps before they have the opportunity to develop into a cancer (see colonoscopy section). Colonoscopy is also the most common way cancers are diagnosed.
Colorectal cancer can cause a variety of symptoms including bleeding, anemia, weight loss, a change in bowel habits or in the pattern and type of bowel movements and, rarely, pain or abdominal distension or bloating. In the U.S. a large proportion of large bowel cancers are detected on screening colonoscopy in patients who do not have any symptoms at all. Other ways that these tumors may be diagnosed are CT scans, PET scans, MRI scans, barium enema or virtual colonoscopy. Rectal cancers that are close to the anus are often discovered on digital examination of the anus which is a routine part of the physical examination carried out by general medical doctors or internists.
After a colorectal cancer has been diagnosed other tests are usually carried out to determine if the tumor has spread to another part of the body. The most common places for a large bowel malignancy to travel (from the most to the least frequent) are the liver, lungs, bone, and the brain. Abdominal and pelvic CT scans, MRI scans, PET scans, or ultrasound examinations are the tests that are most commonly used (usually only 1 test is performed per patient). Also some blood evaluations are usually done including a CEA test (carcinoembryonic antigen). CEA is a cancer marker that most, but not all, colorectal cancers make and that can be found in the blood stream. Rectal cancer, for a number of reasons, is different from colon cancer in regards to the preoperative evaluation prior to treatment (please see the rectal cancer section). The treatment options for colon and rectal cancers will be discussed separately.
Colon Cancer Treatment
Surgical resection is the primary treatment for the majority of colon cancers. Patients with Stage 4 disease are an exception and are usually best treated with chemotherapy initially. In patients that undergo surgery, a segment of the colon (usually 7-10 inches) that contains the tumor and margins of normal colon on both sides of the cancer as well as the lymph nodes and blood vessels that supply the segment is removed. In some patients with multiple lesions or a predisposition to colon cancer formation the majority of the colon (2-3 feet) is removed. In the vast majority of colon cancer resection patients the remaining ends of the bowel are reconnected (anastomosis) so that the patient will go to the bathroom in the usual way (through the anus). In some patients a colostomy or ileostomy (aka stoma) may be necessary but is usually temporary; in this situation the end of the bowel closest to the stomach is brought out through the abdominal wall of the patient and sewn to the skin. A bag or appliance is placed over the stoma to catch the stool which exits the body through this opening rather than via the anus.
Presently, there are several surgical methods that can be used to carry out the colon resection (aka colectomy). Up until the early 90’s the only method available was the “open” method in which bowel resections were carried out through a lengthy incision made in the abdominal wall that provided the surgeon access to the abdominal cavity. The incision is usually a vertical one made in the middle of the abdomen although sometimes a side to side or transverse incision is used. The second method that is now available is called the laparoscopic or minimally invasive method. This method utilizes 4 or 5 small incisions (3/8” to 3/4” in size) through which hollow cylinders called ports are placed. Carbon dioxide gas is pumped into the abdomen through a port and elevates the abdominal wall creating a space within which the surgery is carried out. A long slender telescope with a camera attached is inserted into the abdomen and the operation is done with long thin instruments placed through the other ports. The proven advantages of laparoscopic methods are: 1) less pain, 2) quicker return of bowel function and resumption of oral diet, 3) more rapid discharge home, and 4) better preserved immune function. Please see the Minimally Invasive Surgery Section for a detailed explanation.
After surgery, some patients will be advised to take chemotherapy, usually for a period of 6 months, in order to improve their chances of avoiding a cancer recurrence and to improve their chances of survival. Chemotherapy is recommended for patients who on review of the colon specimen are found to have 1 or more lymph nodes involved with cancer and for some patients with tumors that invade through the entire colon wall. Radiation treatment, except in very rare situations, is not given to colon cancer patients. Currently, there are at least 6 chemotherapy drugs which have been proven to be effective for colorectal cancer. A variety of regimens are being used today (please seen Continuum Cancer Center’s Medical Oncology Section for more details). As mentioned above, most patients found to have metastatic colorectal cancer, with the exception of those who are obstructed or heavily bleeding are initially treated with chemotherapy alone. In these cases, surgery is held in reserve.
Rectal Cancer Evaluation and Preoperative Radiation and Chemotherapy Treatment
The rectum, the part of the large bowel leading to the anus, is about 5 inches long. Cancers in this segment are treated differently than colon tumors. Unlike the colon, two thirds of the rectum is embedded in the pelvic tissue and is situated very close to the vagina and bladder in women and to the prostate and bladder in men. Rectal cancer is harder to cure, in part, because it can more readily spread to these surrounding pelvic organs as well as to the sacrum bone. Also, for rectal cancers that involve the anus or are located very close to the anus it is sometimes necessary to surgically remove the entire anus and rectum and make a permanent colostomy (end of the remaining colon brought out through the abdominal wall). In an effort to improve the survival, reduce the recurrence rates, and to save the anus so that it can then be re-hooked up to the colon, radiation (RT) and chemotherapy (chemo) are often given before surgery. RT and chemo can also be given after surgery; however, it has been proven that it is more effective when given before surgery.
It has been shown in studies of rectal cancer patients that preoperative (preop) RT and Chemo increases the chances of being able to save the anal sphincter and also decreases significantly the chances of the cancer recurring in the pelvis. Preop RT and Chemo can also convert an unresectable tumor into a resectable one. Not all patients are advised to get preop RT and chemo; only patients whose tumors invade through the entire rectal wall into the surrounding tissue OR who have enlarged lymph nodes in the area are given this pre-surgical treatment. In order to determine how far the tumor has invaded and whether there are enlarged lymph nodes one or several tests are done after the rectal cancer has been diagnosed.
The 2 best ways to evaluate rectal cancers are via ultrasound (transrectal ultrasound, TRUS) or magnetic resonance imaging (MRI). The ultrasound examination is done by inserting either a rigid or flexible ultrasound probe into the rectum via the anus and then examining the cancer. The rigid probe is most commonly used in the U. S. . The depth of invasion of the cancer can be determined accurately and enlarged lymph nodes can also be detected. Tumors that invade through the entire wall into the surrounding fatty tissue are called T-3 lesions (T-1 and T-2 lesions invade only partway through the rectal wall). The TRUS exam usually takes 15 to 30 minutes to complete and is well tolerated by most patients. The MRI scan
is done with a large doughnut shaped machine into which the patient is positioned. In addition, for a detailed pelvic examination, a special blanket is usually placed over the patient’s lower abdomen and pelvis. The MRI provides very detailed information including the depth of invasion and the presence of enlarged lymph nodes. The colorectal surgeons at Mount Sinai St. Luke’s Roosevelt Hospital routinely perform TRUS in their offices and MRI examinations are available at Mount Sinai St. Luke’s Roosevelt Hospital.
In addition to the TRUS or MRI done to locally evaluate the cancer, these patients are also evaluated for distant metastases (liver, lung, etc) via CT scans, MRI scans, PET scans, and/or ultrasound examinations, as mentioned earlier.
Surgical Treatment Options for Rectal Cancer
Similar to colon cancer, surgery remains the mainstay of curative treatment for rectal cancer. Presently, worldwide, the great majority of rectal cancers that have not spread to distant sites (liver, lung, etc) are surgically resected through the abdomen using either open (big incision) or laparoscopic methods. A small percentage of rectal cancers are resected through the anus (local excision method) at some hospital centers. These are usually lesions that have not invaded through the entire rectal wall and that are located in the part of the rectum close to the anus but not involving the anal sphincter muscle.
Local Surgical Treatment of Rectal Cancer
As mentioned, transanal local excision is an option for select rectal cancers. In this operation a “disc” of the rectal wall containing the cancer and a margin of the normal rectal wall is resected through the anus. The resulting wound is usually, but not always, closed with sutures. Possible complications include bleeding and infection. This is a far less traumatic operation than the “through the abdomen” radical rectal resection method and can usually be done with a spinal anesthetic. The complication rate is low and patients are usually discharged home within a few days. Unfortunately, local transanal rectal cancer resection is associated with significantly higher local cancer recurrence rates than the radical, through the abdomen, rectal resection. As of 2010, the “gold standard” for curative rectal cancer surgical treatment remains the through the abdomen approach.
In addition to transanal local excision, alternative local treatments for rectal cancer include coagulating or burning the tumor (aka fulguration) or high dose radiotherapy that is applied directly to the tumor through a scope placed through the anus. The local excision method is the most commonly employed local treatment option. As of 2010 local excision is usually combined with preoperative RT and Chemo in an effort to decrease the local recurrence rate. Early results using this approach are promising. Proponents of the RT and Chemo followed by local excision are in the midst of organizing a multicenter trial that they hope will provide data demonstrating that, for select cancers, this approach yields results comparable to those following radical through the abdomen rectal resection.
Through the Abdomen “Radical” Rectal Resection for Rectal Cancer
Trans-abdominal rectal resection remains the treatment of choice and is associated with the highest rate of survival and lowest local recurrence rates. In this operation the tumor along with a margin of normal rectum (and usually some colon as well) is removed in addition to the surrounding lymph nodes and the blood vessels supplying the rectum. The rectal resection method that is the “gold standard” routinely employed in the U.S. and worldwide is called ‘total mesorectal excision’ or TME technique. Operations performed using the TME method when carried out by surgeons experienced with this technique yield the lowest local recurrence rates and the highest 5 year survival rates.
Essentially there are 3 different radical operations for rectal cancer (TME method is used for all). Which operation is performed depends mainly on the distance of the tumor from the anus and the anal sphincter. In order to cure the patient it is necessary that a margin or cuff of normal rectum beyond the tumor (closer to the anus) be excised to ensure that the entire tumor has been removed. As long as there is some rectum left in the patient then it is usually possible to reconnect to remaining colon to the rectal remnant (called an anastomosis) so that the patient can continue to go to the bathroom in the usual way. This operation is called a Low Anterior Resection (LAR).
If the anus is involved with the cancer then it is usually necessary to fully resect the anus, the anal sphincter muscles, and the rectum to safely remove the tumor. In this situation the end of the remaining colon is brought out through a circular opening in the abdominal wall to create a permanent colostomy. Stool then exits the body through the colostomy into an airtight plastic bag that is securely attached to the surrounding skin. This operation is called an Abdominoperineal Resection (APR).
If the tumor is located just above the anus and sphincter such that it is not possible to resect a cuff of normal rectum, in some cases, it may be possible to remove the last inch of the rectal lining while preserving the anal sphincter muscle. The remaining colon can then be sewn to the anal skin in order to permit the patient to go to the bathroom through the anus in the normal way. This operation is called a proctectomy with a coloanal anastomosis (Coloanal).
One important complication that can occur during the first 10 days after surgery in LAR or Coloanal cases is an anastomotic leak. In this situation small amounts of stool leak out between the sutures or staples of the anastomosis into the surrounding pelvis and usually cause an abscess. Patients with leaks usually get quite ill and often require reoperation to drain the abscess and to bring either the colon or the small bowel outside the body through a circular opening in the abdominal wall. The externalized bowel is opened and sewn to the skin edge to create either an ileostomy (small bowel) or colostomy (colon) that redirects or “diverts” the stool to the abdominal wall. This stops the flow of stool to the anus as well as the seepage from the anastomosis and, in most cases, allows the leak to seal. Patients who develop anastomotic leaks are usually in the hospital for at least 2 weeks if not longer. Once the leak seals and the infection fully resolves the ileostomy or colostomy can be closed at a smaller second operation. After closure the patient will go to the bathroom through the anus in the usual way. Unfortunately, bowel function after an anastomotic leak is usually worse (more bowel movements and a decreased ability to store stool) than in patients who heal uneventfully.
In an effort to avoid anastomotic leaks surgeons often make a temporary ileostomy or colostomy (aka ‘stoma’) at the time of the rectal resection and anastomosis. If, from the start, the patient has a stoma diverting the stool away from the bowel rejoining point it is highly unlikely that a leak, abscess or pelvic infection will develop. The average length of stay in patients with a stoma after an LAR or Coloanal is about 6-9 days. The temporary stoma is closed at a smaller second operation (usually less than one hour) that is usually carried out about 2-3 months later.
All 3 radical rectal resection operations (LAR, APR, and Coloanal) can be carried out using either open (big incision) or minimally invasive surgery (MIS) methods. MIS operations are associated with significantly smaller abdominal wall incisions as well as less pain, a quicker bowel recovery, and a shorter hospitalization. Please see the Surgery Technique Section for more information about both MIS and Open operations.