Similarities Between Colon and Rectal Cancer
Besides originating in the large intestine, here are characteristics that colon and rectal cancer have in common:
Symptoms: Since bloody stools are typical for rectal and colon cancer, red or dark-colored spots/streaks may be noticeable with bowel movements. Constipation, gas pain, bloating, and abdominal discomfort are also signs of colon and rectal cancer. Risk factors: Being overweight, smoking, alcohol use, eating a low fiber diet, the presence of polyps, increased age, type 2 diabetes, and family history are risk factors for both colon and rectal cancer. Incidence: Although colon cancer is slightly more prevalent than rectal cancer, combined colorectal cancers are the third leading cause of cancer-related deaths in the United States. In addition, colorectal cancers affect more Black Americans than White Americans. Genetics: Colon and rectal cancer share genetic mutations responsible for their growth, including familial adenomatous polyposis. Screening: Early detection for colon and rectal cancer is essential to early diagnosis and treatment. Colon and rectal cancer screening is the same and includes stool-based tests, visual exams (colonoscopy and flexible sigmoidoscopy), and polyp removal.
Differences Between Colon and Rectal Cancer
Anatomy
Colon and rectal cancers start in different parts of the large intestine. Colon cancers start in the first (and longest) part of the large intestine. Rectal cancers, on the other hand, start in the last several inches of the large intestine.
The blood supply, lymphatic drainage, and nerve supply of the colon and rectum are not the same. In addition, the rectum is close to other organs, and unlike the colon, it lacks a protective outer layer called the serosa. Therefore, metastasis (spread) of disease is more likely to occur with rectal cancer than with colon cancer.
Sex Differences
While colon cancer is fairly equal between the sexes, women are more likely to develop right-sided colon cancer, which is more aggressive than left-sided. A larger number of men than women develop rectal cancer.
Disease Recurrence
When cancer comes back after treatment and surgery, it is called disease recurrence. Cancer can return locally (in the area where it originated) or can be metastatic (spread to other tissues or organs).
Although recurrence rates depend on several factors, two separate studies show that local recurrence of rectal cancer varies from 7% to 21% for rectal cancer versus about 4% to 11% for colon cancer.
Invasion of Nearby Tissue
Cancer cells invade neighboring tissue and organs by entering the bloodstream or the lymph system and traveling to other areas of the body. Since rectal tumors are close to blood vessels, they easily spread. One study found that rectal cancer tends to spread to the thoracic organs (lungs) and the nervous system, whereas colon cancer often spreads to the liver.
Colostomy
People who undergo surgery for rectal cancer have a greater chance of having a permanent colostomy. If the tumor is low in the rectum, the anal sphincter may need to be removed, requiring a life-long colostomy.
Treatment
Surgery: Removing cancer is essential for colorectal treatment. Surgery for colon cancer may be recommended at any disease stage, while surgery without chemotherapy or radiation therapy is typically prescribed for stage I and II colon cancer. In contrast, surgery for rectal cancer is usually performed for stages I-III. Surgical difficulty: Rectal cancer surgery is more complicated than colon cancer surgery, as the rectal tumor can be difficult to access without damaging surrounding structures. Therefore, surgical complications tend to be worse with the removal of rectal cancer. Radiation therapy: Radiation is not commonly used for colon cancer, but most rectal cancers are treated with radiation before surgery to shrink the tumor before removal. Chemotherapy: Chemotherapy is used for both colon and rectal cancer depending on the stage. However, different types of chemotherapy drugs are used for each disease. Targeted therapy: If there is a molecular mutation that is causing the colon or rectal cancer to grow, then medications that target the specific mutation may be available for use in both diseases. Immunotherapy: Medications that destroy cancer cells by increasing immune system response are called immunotherapy. These treatments are available for both colon and rectal cancer. Clinical trials: Finding new cutting-edge therapies can be helpful in the treatment of colon and rectal cancer. Clinical trials can be accessed on the NCI website.
Summary
Colorectal cancer is a term used to describe both colon and rectal cancer. Both cancers affect the large intestine. Cancer cells that develop in the colon are called colon cancer, while cancer cells that grow in the rectum are called rectal cancer.
Although both colon and rectal cancer begin in the large intestine and share similar symptoms, the diseases are treated differently. Screening for rectal and colon cancer is essential to early detection and treatment. Tell your healthcare provider if you have blood in your stool, abdominal pain, or suffer from constipation.
A Word From VeryWell
As our understanding of genetics improves, scientists are finding abnormalities in genes resulting in mutations that drive cancers to grow. Considering these genetic mutations is vital for scientists and future cancer treatment. In addition, finding immunologic and biogenetic approaches that target these unique cells may allow for the disease’s control and even eradication.
