Differences Between Colorectal and Colon Cancer

Despite similarities, outcomes and treatment can vary

Colorectal cancer is a term used to describe rectal cancer and colon cancer. Sometimes believed to be the same disease, there are distinct differences between the two diagnoses. The colon is part of the large intestine and is responsible for reabsorbing fluids and processing waste products. The rectum is the final part of the large intestine that holds feces.

When cancer cells develop in the colon, it is called colon cancer; likewise, it is called rectal cancer when cancer cells develop in the rectum. This article will review the differences and similarities between rectal and colon cancer.

colon vs. rectal cancer
Verywell / Jessica Olah

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 the 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 therapyRadiation is not commonly used for colon cancer, but most rectal cancers are treated with radiation before surgery to shrink the tumor before removal.
  • ChemotherapyChemotherapy 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.

Frequently Asked Questions

  • Do all colorectal cancers start with polyps?

    Most colorectal cancers start with polyps, but some start in the lining of the large intestine.

  • Can an MRI detect colorectal cancers?

    A CT scan is best for detecting colorectal cancers but an MRI is useful in staging colorectal cancers.

  • Are all colorectal tumors cancerous?

    Noncancerous tumors, such as polyps and adenomatous polyps are commonly found in the colon and rectum. Although many benign tumors don't cause symptoms they may need to be removed.

10 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Serenity Mirabito RN, OCN
Serenity Mirabito, MSN, RN, OCN, advocates for well-being, even in the midst of illness. She believes in arming her readers with the most current and trustworthy information leading to fully informed decision making.

Originally written by Lisa Fayed