Fully 95% of all colorectal cancers are adenocarcinomas. Adenocarcinoma is a cancer that arises from the glandular lining, or mucosa of the colon, rectum and appendix. Colorectal adenocarcinoma is the third most common cancer in men and women and second leading cause of death for both men and women in the United States. Colorectal cancers are the most common gastrointestinal (GI) carcinomas.
What are the risk factors for colon cancer?
It is important to understand that while a family history is considered a risk factor for the development of colorectal cancer, greater than 75% of colon and rectal cancers occur in people with no family history. Colorectal cancer may occur at any age, although over 90% of the patients are over age 40 at diagnosis. Following this the risk doubles every 10 years. In addition to age, other high risk factors include:
Males show a slight predominance
Personal risk factors:
-Family history of polyps or cancer
-Personal history of colonic polyps
-Personal history of cancer, especially:
- Breast cancer
- Uterine cancer
- Ovarian cancer
-Inflammatory Bowel Disease
-Chronic ulcerative colitis
-Chronic Crohn’s disease
-Diet high in red meats & animal fats
-Low fiber diet
Inheritable genetic conditions:
-Familial Adenomatous Polyposis
-Herediary Non-Polyposis Colon Cancer
Approximately 10% of cases are linked to insufficient activity. The risk for alcohol appears to increase at greater than one drink per day. There is no absolute risk factor for the development of colorectal cancer; therefore, even though living a healthy lifestyle is helpful, it cannot prevent the development of colorectal cancer entirely. It is for this reason that colorectal cancer screening through colonoscopies is advised.
What causes colon cancer?
Many colorectal cancers are thought to arise from adenomatous polyps in the colon. It is believed that nearly all colon and rectal cancers begin in benign polyps. These pre-cancerous growths occur on the bowel wall, eventually increasing in size and becoming cancer. This sequence can potentially be averted through a preventative colonoscopy.
What are the symptoms of colon cancer?
It is important to understand that the most common symptom of colorectal cancer and polyps is no symptom at all. For this reason, it is important that colorectal cancer screening begin at the age of 50 or starting at 40 for individuals who are experiencing rectal bleeding or have a first-degree relative (parent or sibling) with colon cancer or polyps. The goal is to identify the potential for disease or the condition early, when it is easier to prevent or cure.
Colorectal cancer is known as a “silent” disease, because many people do not develop symptoms, such as bleeding or abdominal pain, until the cancer is difficult to cure. In fact, the possibility of curing patients after symptoms develop is only about 50%. On the other hand, if colorectal cancer is found and treated at an early stage, before symptoms develop, the opportunity to cure is 80% or better.
How is colon cancer diagnosed?
The majority of the time, the diagnosis of early colon cancer is through a colonoscopy. The symptoms of colon cancer to watch out for include any change in bowel habit such as constipation or diarrhea and any blood in the stools. A colonoscopy will often be necessary to obtain a tissue biopsy and confirm the diagnosis of a more advanced colorectal cancer as well, although the initial diagnosis may be made with another modality, such as a CT scan. Additional studies such as a CT scan and a PET scan will typically be done to stage the cancer, especially to evaluate whether the cancer has spread to the lymph nodes or other organs, such as the liver.
The treatment of rectal cancers differs slightly from colon cancer because the rectum is located in the bony confines of the pelvis where there are many closely spaced organs in both men and women. Additionally for the rectum, as the last segment of the large intestine, preservation of the anal sphincters is an important consideration when planning a surgical intervention. Sphincter-sparing surgeries are an important part of the colorectal surgeon’s armamentarium in the fight against rectal cancers while maintaining quality of life for patients.
How is adenocarcinoma of the colon treated?
Colon cancer treatment consists of mainly surgery, and if the cancer is advanced, chemotherapy. Under rare circumstances radiation is also used.
Both colon and rectal cancers are adenocarcinomas and have a similar pattern of spread to lymph nodes. Surgery therefore involves removal of the involved segment of the colon, usually about 12 inches, along with its associated blood supply and lymph nodes. This is followed by reconnection of the bowel to re-establish continuity. This reconnection is called an anastomosis. Surgery can be accomplished with a traditional, open approach or with some of the newer, minimally invasive surgeries, such as laparoscopic and robotic techniques. The operation is performed on an inpatient basis and patients typically are in the hospital for four days after surgery.
In the treatment of colon cancer, it is important to remove all of the cancer in one piece, along with a rim of surrounding healthy tissue, to ensure that none of the cancer is left behind. The lymph nodes are also removed and evaluated. The pathologist will determine how deeply into the colon wall the cancer has invaded, that all of the primary cancer has been removed and if the cancer has developed the ability to spread in a dis-continuous fashion, or metastasize, away from the primary tumor.
What is the prognosis of colon cancer?
In the early stages, surgery may be all that is required for optimal treatment of the cancer; however, if the cancer has spread to the lymph nodes, follow-up chemotherapy will generally be advised. The survival rate for colon cancers detected in the early stages is about five times that of late-stage cancers. Between 80 and 90% are restored to normal health if the cancer is detected and treated in the earliest stages. The cure rate drops to 50% or less when diagnosed in the later stages. Thanks to modern surgical techniques, particularly in the hands of a board certified colon and rectal surgeon, less than 5% of all colorectal cancer patients require a creation of a colostomy.