Cancer is one of the leading causes of death in the United States, and colon cancer is the third most common cancer diagnosed in the United States. Colon cancer affects men and women, and the American Cancer Society estimates that over 97,000 new cases of colon cancer will be diagnosed in the U.S. in 2018. Additionally, over 43,000 new cases of rectal cancer are estimated to be diagnosed. Colon cancer is cancer that starts in the colon, and rectal cancer is cancer that starts in the rectum. Colorectal cancer is a term that refers to cancer that began in either the colon or the rectum.
What Causes Colon Cancer?
Most colon cancers are caused by polyps. Polyps are growths on the colon or rectum and can be malignant or benign. Benign polyps shouldn’t be ignored, though, as they can sometimes become cancerous over time. Polyps are more likely to become cancerous if any of the following applies:
- A polyp is larger than one centimeter.
- More than two polyps are found.
- If dysplasia is present after polyp removal. Dysplasia means that either the removed polyp or the lining of the colon or rectum has a spot where the cells look abnormal but are not considered cancerous cells yet. The abnormal cells make dysplasia a precancerous condition.
Once a polyp is cancerous, the cancer cells can spread from the polyp to the lining of the colon or rectum. From there, it can spread to blood vessels, lymph nodes, and potentially to other parts of the body. Like other cancers, there are four stages of colorectal cancer. There is a stage zero, however, so one could technically say there are five stages. The higher the stage number, the further the cancer has spread in the body.
Colon Cancer Risk Factors
Some people may be at an increased risk of developing colorectal cancer. Factors that contribute to a higher risk for colorectal cancer include age, race, ethnicity, genetics, personal and family medical history, and lifestyle choices.
Colorectal cancer most often occurs after age 50. However, that doesn’t mean that it cannot develop before age 50. Colon cancer can develop at any age.
A personal history of previous colorectal cancer, colorectal polyps, inflammatory bowel disease, or type 2 diabetes increases one’s chances of developing colorectal cancer or getting colorectal cancer again. A family history of colorectal cancer or precancerous polyps also increases one’s chances of developing colorectal cancer. Family history refers to first-degree relatives, meaning parents, siblings, or children who have been diagnosed with colorectal cancer or polyps.
Race and Ethnicity
For reasons unknown, colorectal cancer is most common in the United States amongst African Americans. Globally, Jews of Eastern European descent have a greater risk of developing colorectal cancer than any other ethnic group.
In some cases, colorectal cancer is linked to hereditary syndromes that get passed down in families through genes. Possible hereditary causes of colorectal cancer include:
- Lynch Syndrome
- Familial Adenomatous Polyposis (FAP)
- Peutz-Jeghers Syndrome (PJS)
- MYH-associated Polyposis (MAP)
One cannot change one’s personal medical history, family history, age, or genetics. There are, however, certain lifestyle choices that carry an increased risk of colorectal cancer and can be changed to lower the risk. These include:
- Weight: Being overweight or obese increases the risk of developing colorectal cancer.
- Physical activity: Being active can help lower the risk of colorectal cancer while being inactive increases the risk.
- Diet: Diets that are high in red meats and processed meats increase the risk of developing colorectal cancer.
- Smoking: Smokers are more likely than non-smokers to develop various types of cancer, including lung cancer and colorectal cancer.
- Heavy alcohol use: According to the American Cancer Society, moderate to heavy drinking has been linked to multiple types of cancer, including colorectal cancer.
Colon Cancer Symptoms
Symptoms of colon cancer may not appear right away. By the time symptoms do appear, they often include the following:
- Change in bowel habits:
- Narrower stools
- An urge to have a bowel movement that is not relieved by actually having one
- Rectal bleeding with bright red blood
- Blood in the stool or darkened stool
- Cramping and/or abdominal pain
- Weight loss without change to diet or exercise
- Onset of anemia due to blood loss and bleeding into the digestive tract
Colon Cancer Treatment
The treatment prescribed for colon cancer will depend upon the stage of the cancer. Common treatments include surgery and chemotherapy.
If caught in the early stages, colorectal cancer can sometimes be treated with surgery alone, such as removal of the cancerous polyps. As the cancer progresses, however, more involved surgeries may become necessary, including removing part of the colon. Common surgeries used to treat colorectal cancer include:
- Polypectomy to remove cancerous polyps.
- Local excision to remove cancer from the inside lining of the colon.
- Partial or total colectomy to remove part or all of the colon as well as nearby lymph nodes.
- Surgery to remove small cancer spots on other organs where the cancer has spread.
Chemotherapy is a medical protocol that uses drugs to kill cancer cells. It is a common treatment in many types of cancer, including colorectal cancer. Most patients who have been prescribed chemotherapy usually receive multiple rounds of the treatment and have to wait around two to four weeks between treatments to give their bodies a chance to rest and recover.
Chemotherapy may be given after cancer removal surgery to ensure that no cancer cells are left behind. It can also be given before surgery in an attempt to shrink large tumors. Shrinking large tumors increases the likelihood of successful tumor removal surgery. There are different ways that a patient may receive chemotherapy, including:
- Systemic: drugs are injected or taken orally to get the drugs into the bloodstream and distributed throughout the body.
- Regional: drugs are focused on the specific part of the body that is housing the tumor or cancer cells.
Common side effects of chemotherapy include:
- Hair loss
- Mouth sores, or ulcers
- Decreased appetite
- Nausea and vomiting
- Reduced white blood cell count, which increases the likelihood of infections
- Reduced blood platelets which increases easy bruising and bleeding