Colorectal cancer is the second leading cause of cancer related death and one of the most preventable. The lifetime probability of an average person developing colorectal cancer is 6% (or about one in 20). It is estimated that 14% of all cancers diagnosed each year occur in the colon or rectum. This translates into an estimated 1,38,000 cancers. Nearly 60,000 people die of colorectal cancer each year.
WHO IS AT RISK ?
The exact cause of colorectal cancer is unknown. Physicians often cannot explain why one person develops this disease and another does not. However, the understanding of certain genetic causes continues to increase. The following factors can increase the risk of colorectal cancer.
- People diagnosed with colorectal cancer, 90% are over the age of 50
- Family history of colorectal cancer (especially parents or siblings)
- Personal history of Crohn’s disease or ulcerative colitis for eight years or longer
- Personal and family history of colorectal polyps
- Personal history of breast, uterine or ovarian cancer
HOW DOES IT START ?
Most colon and rectal cancers develop from a single cell or group of cells in the lining of the bowel. These cells start to multiply and grow into a non-cancerous (benign) growth called a polyp. Polyps appear as elevations or projections on the lining of the bowel wall. As they increase in size, they may become cancer with the potential to invade through the bowel wall or spread to other sites in the body. The change of a benign polyp into a cancerous tumour appears to be associated with changes or mutations in the genes that control each cell. These changes may be inherited or may occur spontaneously.
WHAT ARE THE SYMPTOMS?
Colorectal cancer is usually asymptomatic in its early stages and is detected during routine screenings. It is important to note that other common health problems can cause some of the same symptoms. For example, hemorrhoids are a common cause of rectal bleeding, but do not cause colorectal cancer. Colorectal cancer symptoms include:
- A change in bowel habits: constipation, diarrhea, frequency of the bowel movements
- Narrow/smaller shaped stools
- Bright red or very dark blood in the stool
- Ongoing abdominal or pelvic pain and bloating
- Unexplained weight loss
- Nausea or vomiting
- Feeling tired all the time
Abdominal pain and weight loss are typically late symptoms, indicating possible extensive disease. Anyone who experiences any of the above symptoms should see a physician as soon as possible.
People who have a family history of colorectaJ cancer or polyps or a personal history of colorectal cancer or adenomatous polyps should have a colonoscopy. Any polyp should be removed and the examination repeated in one to three years.
If the exam is normal, then colonoscopy should be repeated every three to five years. Women with a personal history of breast, ovarian or uterine cancer should also have colonoscopy every three to five years beginning at age 40.
HOW DOES COLORECTAL CANCER SPREAD?
Cancer has two ways of spreading: by direct growth of the tumour and by distant spread of cancerous cells called metastases.
Direct growth: As these tumours grow, they may spread into or around the bowel. Eventually, they will invade the bowel wall and spread into adjacent organs, such as other loops of intestine, the abdominal wall, the bladder, or the uterus.
Metastases: Lumps of cells may break off from the primary tumour and spread to other parts of the body through the blood stream or through the lymph fluid that bathes the cells. These cells grow at distant sites such as the lymph nodes around the bowel, the liver or the lungs. When a colorectal cancer is surgically removed, the lymph nodes in the tissue around the tumour are also removed. The pathologist then looks at the nodes under a microscope to see if they contain any tumour cells. If there are no tumour cells in the lymph nodes, chances for a cure are better.
HOW ARE CANCERS OF THE COLON & RECTUM TREATED?
These cancers are removed surgically. An operation is usually performed through an abdominal incision. The section of bowel containing the cancer along with the associated blood vessels and lymph nodes are removed. In most cases, the bowel is put back together or recormected so that normaJ bowel ftmction is restored. This reconnection is called an "anastomosis." If the cancer has spread to the lymph nodes or elsewhere, additional (adjuvant) treatment such as chemotherapy / radiotherapy may be suggested.
Cancers of the rectum develop in the lower six inches of the large bowel above the anus. There are more options for treating these tumours. Larger, non cancerous polyps and some early cancers may be removed through the anus. Most of the larger cancers are removed surgically through the abdomen. Although the bowel is usually reconnected after surgery, removal of the entire rectum and anus may be occasionally necessary when the cancer is located very close to the anal opening. In this situation, a colostomy is created. This is an opening of the bowel through the skin of the abdominal wall. In rare instances, a temporary colostomy may be required if the cancer blocks the bowel. Today, most colorectal cancers can be treated without a colostomy.
WHAT IS STAGING AND WHY IS IT IMPORTANT?
Staging provides a way to estimate the chance of a cure after a cancer has been removed. Unlike other solid tumours, the size of the colorectal cancer has little influence on the possibility of cure. A staging system helps the doctor evaluate the tumour based on: if it has grown into the bowel wall; if it has spread into nearby lymph nodes; and, if it has spread to distant organs or tissues. Tumors are classified as Stage I, ll, III or IV. Staging is important because it can help predict chances of survival and guide additional treatments. If a colorectal cancer recurs, it will usually do so within two years of surgery. The vast majority recur within five years. The best chances for a cure, or the best outcome is associated with Stage I cancers with more than 90% of these patients surviving five years after surgery. The appearance of tumour cells under the microscope is also significant in determining the treatment.
This appearance is called "differentiation" tumours are generally classified as well, moderately, or poorly differentiated. Patients with well differentiated tumors have a better outcome than those with poorly differentiated tumours. Staging and differentiation help physicians decide whether to recommend radiation therapy and/or chemotherapy in addition to surgery.
WHAT IS THE LONGTERM OUTCOME OF THE TREATMENT?
Patient outcome is strongly associated with colorectal cancer stage at the time of diagnosis. Cancer confined to the lining of the colon is associated with the highest likelihood of success. This is one reason why early detection through screening methods like colonoscopy is crucial.
Follow-up care after treatment for colorectal cancer is important. Even when the cancer appears to have been completely removed or destroyed, the disease may recur. Undetected cancer cells can remain in the body after treatment. Your colon and rectal surgeon will monitor your recovery and check for cancer recurrence at specific intervals. Most patients will have a repeat colonoscopy one year after completion of treatment. Blood tests, clinical examinations and imaging tests may be performed based on the stage of the cancer.
WHO IS A COLON & RECTAL SURGEON?
Colon and rectal surgeons are experts in the surgical and non-surgical treatment of diseases of the colon, rectum and anus. They have completed advanced surgical training in the treatment of these diseases as well as full general surgical training. They are well-versed in the treatment of both benign and malignant diseases of the colon, rectum and anus and are able to perform routine screening examinations and surgically treat conditions.
