The colon has four sections: The ascending colon extends upward on the right side of the abdomen. The transverse colon goes across the body to the left side. The descending colon continues downward on the left side. The sigmoid colon, named for its S-shape, connects to the rectum, which in turn joins the anus, where waste matter passes out of the body.
Pictures courtesy of Three River Endoscopy
Colonoscopy enables specialists to directly examine most of the colon and rectum of a patient suspected of having developed a colorectal tumor. The top image shows a normal colon; the middle image, a polyp, and at the bottom, a malignant tumor.
Cancer of the large intestine (colon) and rectum,
collectively termed colorectal cancer, is the third most common form of cancer, behind
lung and breast cancer. Each year, approximately 140,000 Americans develop colorectal
cancer, and more than 50,000 people die of the disease. Most of those who die of the
disease suffer from metastases — tumors that spread from the primary bowel
tumor to the liver, pelvic organs, or lungs.
Colorectal cancer affects men and women with nearly equal frequency. One in 25 American
adults develops colon cancer. Most patients diagnosed with colorectal cancer are 65 years
of age or older.
Cancers of the colon and rectum usually arise from growths called polyps. Only a
small fraction of polyps become cancerous, and most grow so slowly that most people are
unaware of them.
Risk Factors
Colorectal cancer seems to occur most often among people who consume diets high in fats and starches, and low in fiber. Another risk factor associated with colorectal cancer is a strong family history of the disease—specifically, genetics.
Silent or Symptomatic
Colorectal cancer can proceed to an advanced stage without any distinctive signs—four or more years. Symptoms may include diarrhea, abdominal discomfort, constipation, or nausea. Other symptoms include a thin or flat stool. Blood — either clearly visible or detectable with special tests — may also be present. The stool may appear reddish, dark cranberry or even black in color. In advanced colon cancer, symptoms may include weight loss, abdominal pain caused by the obstruction of the intestine, and loss of appetite. Some patients feel "weak" and are diagnosed with anemia due to hidden bleeding. Tumors occurring lower in the large intestine (the regions called the sigmoid and rectum) may result in blockages or clearly apparent bleeding.
How is Colorectal cancer DIAGNOSED, STAGED & MONITORED?
Colorectal cancer is almost always diagnosed by observation through a colonoscope (a flexible fiberoptic or TV instrument capable of viewing most of the large intestine). In addition to viewing, colonoscopes permit specialists to snare polyps or tumor fragments for lab analysis. In very early cancer, confined to the top of a small polyp, no additional surgery may be necessary. In some cases, you may also receive a barium enema, which can show areas of the large intestine not visible to the colonoscope. Colonoscopy and barium enema require flushing all bowel contents well before the procedures.
CT
Your physician may also order a "CT" (Computed Tomography) scan. A CT scanner uses x-rays to make images of internal organs and can sometimes detect tumors outside the bowel.
Staging
"Staging" describes how far the cancer may have spread.
In early (Stage A) disease, potential for surgical cure is virtually 100%.
In advanced (Stage D) disease, chances for cure are low. All staging is tentative
until confirmed after surgery, but new imaging techniques can help doctors stage patients
before surgery, and to determine the extent of surgery and postoperative care appropriate
for each patient.
Monitoring
Almost half of all patients thought "cured" of colon cancer develop recurrence within 5 years — usually due to undetected metastases. Therefore, all patients with a history of colorectal cancer should be monitored by experts in GI cancers at least once a year, for life. The same tests used for diagnosis and staging are used for monitoring recurrence — plus a CEA blood test, which detects a protein expressed by colorectal tumors. Newer imaging tests can pick up recurrent metastatic disease earlier, while most curable.
hat is a CEA-ScanŽ (arcitumomab) study? This CEA-Scan image shows normal organs and a wide range of tumors that can be detected by this nuclear imaging study.
The CEA-ScanŽ (arcitumomab) study was specifically developed to detect metastatic disease in patients with primary or recurrent colorectal cancer. In pivotal trials at major cancer centers around the U.S., it has proven capable of detecting metastatic disease earlier than the standard tests used to diagnose and monitor patients with colorectal cancer. Just two years after introduction in the U.S., CEA-Scan data is just now beginning to suggest that such detection can guide surgeons to more curative operations.
The CEA-Scan study is a nuclear medicine procedure — that is, it uses a small dose of radioactive isotope to image tumors sometimes invisible to other diagnostic tests. That isotope is guided to tumors via antibody fragments engineered to seek out and attach to any tissue that expresses carcinoembryonic antigen (CEA), a protein found on virtually all colorectal tumors. CEA blood tests attempt to detect this same protein in blood, but often fail to do so, due to lack of sensitivity.
About three hours after injection of CEA-Scan, imaging begins, and takes two to three hours. CEA-Scan is very safe. In pivotal trials, only 8 of more than 300 patients developed minor, self-limiting adverse events. One severely hypertensive patient reported an apparent grand mal epileptic seizure. Fewer than 1% of patients experienced elevated HAMA (human antimurine antibodies). CEA-Scan is at least as safe as the other studies you will receive. Ask your nuclear medicine specialist about your CEA-Scan.
This CEA-Scan image above shows normal organs and a wide range of tumors that can be detected by this nuclear imaging study.
How is colorectal cancer treated?
Surgery is the only treatment for colorectal cancer with potential for cure. However, operations for colorectal cancer are very major procedures, with varying degrees of risk, depending on the amount of tissue that must be moved, and the ability of patient heart and lungs to withstand the stress of a major abdominal procedure. When patients are otherwise healthy and have very early, local disease, operative procedures are quite straightforward, and within the skills of most board-certified general surgeons. Most of the 140,000 patients with new primary colorectal cancer are treated by general surgeons.
However, when metastatic disease is suspected, or detected during the operation, colorectal surgery can prove very challenging. Board-certified colorectal surgeons are trained to perform more extensive surgery, removing more potentially malignant lymph nodes. They are also trained to use preoperative radiation therapy and smaller margins around the cancerous area, reducing the need for a permanent colostomy. When liver metastases are known or discovered, a second operation by a board-certified surgical oncologist may be necessary to maximize the potential for a cure.
Postoperative adjuvant chemotherapy and radiation therapy — often guided by CEA-Scan studies — promise to enhance each patient’s chance for the longest possible disease-free life. For that reason, patients with a newly diagnosed tumor or a history of colorectal cancer should seek care at a hospital with a well-coordinated team of surgeons, GI specialists, nuclear medicine specialists and medical and radiation oncologists.
When surgery cannot be curative because of extensive metastases, such teamwork can add months or years of qualify life, even when the ultimate prognosis is poor.
What is the prognosis of colorectal cancer?
Probably the most difficult question a patient with colorectal cancer can ask his or her doctor is, "What’s my prognosis?" Many variables only loosely related to the cancer can make a big difference in response to surgery, chemotherapy and radiation therapy — all of which are very demanding, and with potentially life-shortening risks.
As these statistics demonstrate, prognosis depends very heavily on detecting the precise extent of disease, removing as much as possible by surgery, and treating aggressively any disease that may escape detection, or resist surgery. Thus, prognosis depends heavily on detection of all of the patient’s disease, and starting appropriate therapy early. It also depends on assisting patients to withstand those new treatments with scientific nutrition, modern anti-nausea drugs, and other technologies.
Result: Prognosis is constantly improving, even for patients with very advanced disease.
How should you select a colorectal cancer specialist & hospital?
In each area, at least one hospital has organized the multidisciplinary team and state-of-the-art diagnostic and therapeutic resources necessary for optimum treatment and monitoring of patients with colorectal cancer.
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