Colorectal Cancer FAQ
- What is colorectal cancer?
- How common is colorectal cancer?
- What are the major risk factors?
- How does it start?
- What are the signs and symptoms?
- How is it diagnosed?
- How is colorectal cancer treated?
- What is staging?
- How is colorectal cancer staged?
- What is the survival rate?
What is colorectal cancer?
Colorectal cancer (CRC) 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.
It 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 - the S-shaped colon which joins the rectum, which in turn joins the anus, or 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 develop 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. There, 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 (ACS), colorectal cancer is the third most common cancer in both men and women, and the second leading cause of death from cancer in North America. It will strike approximately 174,000 people and cause nearly 61,000 deaths in 2008 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 are diagnosed in individuals 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 ACS, the risk of colorectal cancer increases with age (being older than 50 years of age); 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 colon cancers. Following screening guidelines can lower the number of cases of the disease by detecting and removing 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:
- Diet – cut down on red meats and increase intake of fruits and vegetables
- 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 diary products
How does it 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 polyps is one aspect of preventive medicine that really works.
What are the signs and symptoms?
The American Cancer Society (ACS) 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 ACS recommends that your routine physical include a colorectal cancer detection procedure once you reach age 50. Those detection methods 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 barium enema 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.
How is colorectal cancer treated?
Surgery, radiation therapy and chemotherapy are methods used to treat colorectal cancer, depending on the stage of the disease. Colorectal cancer requires surgery in nearly all cases. Radiation and chemotherapy are sometimes used in addition to surgery. Recurrence rates can be decreased with earlier intervention.
What is staging?
The stage of cancer is an indication of how much the cancer has spread. It is based on a number of criteria, the most important of which is metastasis to the lymph nodes. A patient who has cancer confined to the tumor without spread to the lymph nodes or other organs is classified as either a stage I or II. As soon as there is evidence that the cancer has spread to the lymph nodes, the patient is categorized as stage III.
The staging is important because it determines the course of treatment. Generally, guidelines do not call for adjuvant chemotherapy in patients with stage I or II colon cancer. However, adjuvant chemotherapy is suggested for patients with stage III colon cancer.
How is CRC staged?
At the time of surgery, the tumor and accompanying lymph nodes are removed and sent to the pathology lab for histological examination. The pathologist will microscopically examine one or more thin sections taken through each lymph node for evidence of cancer.
Previstage™ GCC is more accurate than traditional methods for the staging of CRC. Traditional methods are subject to sampling errors since generally only a single 5 µm section of each lymph node is examined by the pathologists. This amounts to less than 0.1% of the lymph node sampled for the spread of cancer.
Previstage™ GCC examines the entire portion of the lymph node submitted (whole or half-node) and utilizes a molecular technique (quantitative RT-PCR) to detect and measure the amount of GCC mRNA (a biomarker for colorectal cancer) in the lymph node.
What is the survival rate?
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 tested, 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%.