Learning about Colorectal Cancer
- What is colorectal cancer?
- How common is colorectal cancer?
- What are the major risk factors?
- How does colorectal cancer start?
- What are the signs and symptoms of colorectal cancer?
- How is colorectal cancer diagnosed?
- What are the colorectal cancer treatment options?
- What is colorectal cancer staging?
- What is the survival rate of colorectal cancer patients?
- How can I learn more ?
What is colorectal cancer?
Colorectal cancer is cancer of the colon or rectum. It is curable if caught early enough. Proper staging is important to determine the extent of cancer involvement and if therapy is warranted.
Colorectal cancer develops in the colon, the first and longest section of the large intestine, or the rectum, the final six inches of the large intestine. The colon has four sections:
- The ascending colon begins where it attaches to the small intestine and 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 is the S-shaped colon that joins the rectum, which in turn joins the anus (the opening where waste (fecal) matter passes out of the body).
The colon and rectum have several layers of tissue. Colorectal cancer starts in the innermost layer and can grow through some or all of the other layers. The penetration of the cancer through these layers will dictate the course and severity of the cancer. It is believed that colorectal cancer begins as polyps, also known as adenoma, and develops slowly over a period of several years. Once a cancer forms in these polyps, instead of growing only into the center of the lumen of the colon or rectum, it will also grow into the wall of these organs. Cells from the tumor can then break away and spread through the bloodstream or lymphatic system to other parts of the body. Therefore, they may form "colony" tumors. This process is called metastasis.
How common is colorectal cancer?
Incidence of Colorectal Cancer Worldwide
| New Cases | Deaths | |
|---|---|---|
| United States and Canada | 174,000 | 61,000 |
| European Union | 280,000 | 139,000 |
Sources: American Cancer Society, Canadian Cancer Society and European Society for Medical Oncology
According to the American Cancer Society, colorectal cancer is the third most common cancer in both men and women, and is the second leading cause of death from cancer in North America. It strikes approximately 174,000 people and causes nearly 61,000 deaths annually in the United States and Canada. It accounts for about 10% of all cancer deaths. That figure is staggering when you consider the disease is potentially curable if diagnosed in the early stages. Though colorectal cancer may occur at any age, more than 90% of the patients diagnosed are aged 50 years and older.
What are the major risk factors?
Anything that increases the chance of having a disease is called a risk factor. According to the American Cancer Society, the risk of colorectal cancer increases with age (being older than 50); risk is also increased by certain inherited genetic mutations [Familial Adenomatous Polyposis (FAP) and hereditary non-polyposis colorectal cancer (HNPCC)], a personal or family history of colorectal cancer and/or polyps, or a personal history of chronic inflammatory bowel disease.
Although the exact cause of most colorectal cancer is unknown, it is possible to prevent the majority of them. Following screening guidelines can lower the number of cases of the disease by detecting and removing rectal or colon polyps that could become cancerous and can also lower the death rate from colorectal cancer by finding disease early, when it is highly treatable.
People can take control and reduce their cancer risk by making some positive lifestyle changes:
- Cut down on red meats and increase intake of fruits and vegetables.
- Increase physical activity. Even small amounts of exercise on a regular basis can have a major impact, at least 30 minutes a day or even walking 3 hours a week.
- Maintain a healthy weight.
- Limit intake of alcohol.
- Stop smoking.
- Increase calcium intake through supplements or low-fat dairy products.
How does colorectal cancer start?
Nearly all colon and rectal cancers begin in benign polyps. These premalignant growths occur on the bowel wall and may eventually increase in size and become cancerous. Removal of benign colorectal polyps is one aspect of preventive medicine that really works.
What are the signs and symptoms of colorectal cancer?
The American Cancer Society states that early colon cancer usually has no symptoms. Signs and symptoms typically occur only when the cancer is more advanced. The absence of symptoms should never be a reason to delay or ignore colon cancer testing.
The most common symptoms are rectal bleeding and changes in bowel habits, such as constipation or diarrhea. These symptoms are also common in other diseases so it is important you receive a thorough examination should you experience them. Abdominal pain and weight loss are usually late symptoms indicating possible extensive disease.
Since many polyps and early cancers fail to produce symptoms, the American Cancer Society recommends that your routine physical include colorectal cancer screening procedures once you reach age 50. These procedures are a digital rectal exam and a chemical test of stool for blood (fecal occult blood test-FOBT). A sigmoidoscopy (the inspection of the lower bowel with a lighted tubular instrument), a colonoscopy (the inspection of the full colon with a lighted tubular instrument), or a double-contrast barium enema (complete radiological examination of the colon) should be part of routine physical check-ups.
How is colorectal cancer diagnosed?
It is widely accepted that the overwhelming majority of colorectal tumors arise from polyps in the colon and rectum. Polyps are abnormal projections of tissue that protrude inside the bowel. They are most frequently found by diagnostic/screening procedures (sigmoidoscopy for the lower intestine or colonoscopy for the entire intestine). If polyps are found during these procedures, they are removed and sent to a pathology laboratory for sectioning and microscopic examination. If the pathology report confirms the presence of cancerous cells, surgery is scheduled to remove the tumor and surrounding area of the colon. At the same time, lymph nodes from the surrounding area are also usually removed for examination to determine if the cancer has begun to spread (metastasized) into the lymph system.
What are the colorectal cancer treatment options?
Surgery, radiation therapy and chemotherapy are methods used to treat colorectal cancer, depending on the stage of the disease. Colorectal cancer surgery is required in nearly all cases without distant organ metastasis. Radiation and chemotherapy are sometimes used in addition to surgery. Recurrence rates can be decreased with appropriate intervention.
What is colorectal cancer staging?
The stage of the cancer is a way to describe its severity. It reflects several factors, such as the size and depth of the tumor penetration into the colorectal wall, whether cancer cells are detected in the surrounding lymph nodes, and whether the cancer has spread to distant organs, such as the lung or liver.
Stages I and II are typically considered “cured” after surgery and require no further treatment. Stage III patients usually benefit from additional treatment after surgery, such as chemotherapy, as cancer cells have been detected in the lymph nodes removed during surgery. Stage IV patients typically do not have surgery and may have other types of treatment.
One particular area in question with the staging of colorectal patients is whether stage I and II patients should get additional treatment after surgery. While initial testing of the lymph nodes has not detected cancer cell clusters, studies have shown that up to 30% of these patients experience a recurrence of their cancer, presumably due to cancer metastases missed during the testing.
Lymph node testing currently involves microscopic examination in which one or more thin slices of each lymph node are examined. This represents less than 1% of the available tissue, leaving 99% unexamined. Further, microscopic testing can detect only one cancer cell in 200 normal cells.
Fortunately, breakthroughs in genetic testing are opening options that test the lymph nodes with much greater sensitivity. The Previstage™ GCC Colorectal Cancer Staging Test examines 50% or more of each lymph node using a molecular testing technique that can detect one cancer cell in 10 million normal cells. That is a 100,000 times improvement in sensitivity across a much larger sample of your lymph node, thus significantly increasing the chance of detecting any cancer cells that have spread from the tumor and providing more accurate information for making critical treatment decisions.
See Understanding Staging for more details about lymph nodes and their role in determining your prognosis.
What is the survival rate of colorectal cancer patients?
According to the American Cancer Society, the 5-year survival rate is 90% for people whose colon cancer is found and treated at an early stage. But because many people are not being screened early, only 39% of colon cancers are found at that early stage. Once the cancer has spread to nearby organs or lymph nodes, the 5-year survival rate goes down to 68%. For people whose colon cancer has spread to distant parts of the body, such as the liver or lungs, the 5-year survival rate is about 10%.
According to recent studies, a variety of factors influence survival rate, such as the location of the tumor in the colon, the number of lymph nodes examined, bowel perforation, bowel obstruction, and the stage and grade of the tumor. Adjuvant treatment, when recommended after surgery, has been shown to improve the chances of survival in most patients. A doctor considers the variety of factors to decide if a particular patient may benefit from additional treatment beyond the initial surgery.
How can I learn more?
This section provided a brief overview of colorectal cancer. Visit our section on Getting Help for access to other organizations and resources.