Colorectal cancer, one of the most deadly forms of cancer in the United States, kills over 50,000 people each year, and every year, there are 140,000 new diagnoses. Since March is National Colorectal Cancer Awareness Month, it’s a great opportunity to learn about the disease, what causes it, and what can be done to prevent it. In addition to raising awareness about colorectal cancer, the month of March is also a chance to encourage others to get a cancer screening from a gastroenterology clinic like Needham Gastro. After all, the survival rate is an amazing 90% when a doctor can catch it early.
What Does the Colon Do?
Understanding colorectal cancer and the risks it poses to the body starts with understanding the colon and its role in the digestive process. The terms colon and large intestine are used interchangeably, but technically the colon is the largest part of the large intestine, along with the cecum, rectum, and anal canal. The colon itself is further subdivided into the ascending colon, transverse colon, descending colon, and sigmoid colon, and these segments wrap around the small intestine and sit just under the liver.
Long before the colon plays its part for digestion, though, the process starts with food being mashed up by the mouth and sent down the esophagus to the stomach. In the stomach, food is subjected to digestive juices and powerful muscle contractions where it becomes a semi-liquid substance called chyme. The chyme then moves to the small intestine where it further subjected to enzyme-rich digestive juices from the pancreas and liver. It is in the small intestine where most of the absorption of nutrients occurs; enzymes break down the chyme into usable components that are then carried away by the bloodstream to be used all over the body.
By the time this digested material makes its way into the large intestine, it is composed mostly of waste products and undigested bits of food. The colon’s part in the process primarily involves absorbing water and salts as bands of muscle push the chyme along. Though the colon doesn’t actually produce digestive enzymes, the gut flora that thrives in the colon can use some of the waste products to synthesize important vitamins. As the material approaches the sigmoid colon, it has formed into a mostly solid stool that will soon be ready to be expelled through the anal canal.
What is Colorectal Cancer?
Colorectal cancer refers to the development of cancer in the colon or rectum; the term is generally used to refer to cancer in either the colon or rectum since both conditions are similar in the way they progress and present. In this type of cancer, abnormal growth of cells begins in the colon or rectum; over time, this cancerous mass causes cell death in the tissues of the colon that leads to a variety of symptoms and loss of colon function. As with all types of cancer, it can also eventually spread to other parts of the body.
The starting point for colorectal cancer is usually polyps, small growths on the inner lining of the colon or rectum. Though many polyps are benign at first, some types can eventually become cancerous. Two types of polyps- hyperplastic polyps and inflammatory polyps (that are typically associated with inflammatory bowel disease), have very low malignancy potential and therefore are very unlikely to lead to cancer. Adenomatous polyps are a type referred to as precancerous, and they are much more likely to lead to colorectal cancer.
The symptoms of colorectal cancer often don’t present until the disease is further along, and they also are similar to various common digestive diseases like irritable bowel syndrome, hemorrhoids, or inflammatory bowel disease. For this reason, the diagnosis of colorectal cancer is not reliant on the presence of specific symptoms. However, when symptoms do present, there are several typical examples:
- Abdominal pain or cramping
- Unexpected weight loss
- Fatigue or weakness
- Blood in stool
- Rectal bleeding
- Changes in bowel habits for more than a few days
What Causes Colorectal Cancer?
The full cause of colorectal cancer, as with cancer in general, is not fully known yet. Some risk factors have been identified that seem to make it more likely, but the precise mechanism of these factors isn’t fully understood. What scientists do know, however, is that cancer begins from mutations in our cellular DNA. The key genes that appear to be involved are oncogenes, which control cell division, and tumor suppressor genes, which regulate excessive cell growth. When these genes are mutated, their ability to control the kind of cellular overgrowth inherent in cancer is compromised.
It is thus far unclear what causes these mutations in the first place, but the two main possibilities are inherited or acquired. While seemingly rarer, some mutations can come from genes passed on by a person’s forebears; one example is familial adenomatous polyposis (FAP), a condition that involves the development of numerous adenomatous polyps. What is more likely, though, is that these mutations are acquired during one’s lifetime and therefore can’t be passed on to children. In either case, the mutation of the APC gene, one type of the cell-growth regulating tumor suppressor genes, is frequently the starting point for the mutation that leads to cancer.
Colorectal Cancer Risk Factors
Since the cellular mutations that lead to colorectal cancer are more likely acquired during life, the risk factors involved are an important part of determining both who is likely to get it and how to prevent it. The American Cancer Society has identified a series of risk factors that suggest a higher likelihood of developing colorectal cancer:
- Lifestyle Factors
- Heavy alcohol consumption
- Inactivity and lack of exercise
- Diet high in processed or red meats
- Overweight or obesity
- Inherent Factors
- Age (50 years or older)
- Personal or family history of colorectal cancer
- Inflammatory bowel disease
- Type 2 diabetes
- Inherited condition (like FAP or Lynch syndrome)
- Racial and ethnic background, African Americans and Jews of Eastern European descent have the highest risk
Treatment Options for Colorectal Cancer
The treatment for colorectal cancer is highly dependent on the progression of cancer and when it is diagnosed. In order to distinguish between different states of progression, and to organize the treatment options, doctors use a “staging” system that ranges from stage 0 (very early) to stage IV (very advanced).
- Stage 0
- Status: Cancer is confined to polyps or small tumors in the mucosal lining of the colon
- Treatment: Surgery to remove polyps or tumors is standard; a partial colectomy (removal of part of the colon) may be an option in certain circumstances
- Stage I
- Status: Cancer is confined to the colon, but it has grown partly into the colon wall; hasn’t spread to the lymph nodes
- Treatment: Surgery to remove tissues with cancerous cells is still standard; may also include a partial colectomy depending on the spread through the colon
- Stage II
- Status: Cancer is still confined to the colon or nearby tissues, but it hasn’t spread to the lymph nodes
- Treatment: Chemotherapy or a partial colectomy are options depending on the amount of spread and the chances of cancer returning after surgery
- Stage III
- Status: Cancer has spread to nearby tissues and the lymph nodes, but it hasn’t spread to distant parts of the body
- Treatment: Chemotherapy and a partial colectomy are both standards at this stage; radiation therapy may also be used for some patients who aren’t healthy enough for surgery
- Stage IV
- Status: The most advanced stage, where cancer has spread to distant parts of the body through the bloodstream
- Treatment: Surgery may still be used, but it will be combined with chemotherapy
It’s Time to Schedule a Screening If you are between the ages of 45-50 and haven’t yet been screened for colorectal cancer, the time is now. Thanks to National Colorectal Cancer Awareness Month, more people than ever before are taking the necessary steps to get checked and potentially avert a devastating illness. If you would like to speak with a qualified gastroenterologist about scheduling a screening, contact Needham Gastro to make an appointment.