Other Asbestos-Linked Cancers: Colon Cancer

For decades, researchers have known that asbestos exposure damages cells’ DNA, resulting in respiratory illnesses like mesothelioma and asbestosis. Then, as studies continued, other cancers linked to the hazardous fiber started to increase. Now, other known cancers caused by asbestos include ovarian, lung, laryngeal, and colon cancer. Colon cancer, in particular, took years to establish as an asbestos-linked disease.

Colon cancer is a group of cancers with tumors that start in the colon (also known as the large intestine; the last segment of the digestive system). In the U.S., it is the third-most-common cancer (excluding skin cancer). Sometimes, this form of cancer is referred to as colorectal cancer (a combination of colon and rectal cancer).

Rectal cancer is a group of cancers that begins in the rectum, the last segment of the colon ending at the anus. Typically, colorectal cancer starts with the formation of benign (noncancerous) polyps. For most patients, the polyps are small and don’t cause any noticeable symptoms. Subsequently, doctors recommend regular, early screening appointments for cancers of the colon and rectum.

Risk Factors and Causes

Early screening for colon cancer is important for people with a high risk of developing the disease. Risk factors such as age, preexisting digestive disorders, family history, and lifestyle affect who has greater chances of getting cancer. Additionally, some risk factors may also be one of the causes of an individual’s colorectal cancers.

Risk factors for colon cancer include:

  • African American ancestry: Occurrences of colon cancer are higher among African Americans.
  • Age: Adults over the age of 50 have an increased risk.
  • Asbestos exposure: Living or working in proximity to disturbed asbestos fibers can lead to colorectal cancers.
  • Diabetes: Insulin-resistant patients and those with diabetes are more likely to get colon cancers.
  • Diet: Research has found that diets high in fat and low in fiber are linked to colorectal tumors.
  • Family with colon cancer: People are at a higher risk for colon cancer if more than one relative has been diagnosed with it.
  • History of colorectal polyps: Having polyps in the colon or rectum (even if they were removed) puts an individual at greater risk.
  • Inflammatory intestinal disease: Digestive disorders like ulcerative colitis and Crohn’s disease that cause inflammation in colon cells can lead to cancer.
  • Lifestyle: Individuals who fail to exercise regularly and lead sedentary lifestyles have a greater risk. Smoking cigarettes and drinking alcohol is also a lifestyle risk.
  • Obesity: In addition to an increased risk of colon cancer, obese patients are more likely to die of cancer.
  • Radiation treatment: Patients who have had radiation therapy on their abdomen may have an increased risk.

Though the rate of death from colorectal cancers has fallen over the years, it is still among the most commonly diagnosed cancers in the country. In 2020, the American Cancer Society estimates 104,610 new colon cancer cases and 43,340 new rectal cancer cases. The lifetime risk for getting cancer of the colon or rectum is about 4.4 percent for men and 4.1 percent for women.

Cancer researchers have yet to discover the precise cause of colon cancer but are able to identify mutations in cells’ DNA that indicate a precancerous cell. Regular colon screenings – for high-risk individuals – can catch these mutations early before the person has any symptoms. The 3 screening tests recommended by the National Institutes of Health for colorectal cancers are:

  • Colonoscopy: Using a camera attached to a thin tube, doctors can inspect the entire colon from the inside. It is the most accurate test. Recommended every ten years.
  • Flexible sigmoidoscopy: This procedure uses equipment similar to a colonoscopy but inspects only the sigmoid and rectum areas of the colon (i.e., the lower sections). Recommended every five years.
  • Home stool test: At home, patients collect a sample of their stool using a kit from their doctor. The kit is then mailed to a lab for testing. Stool tests can signal the need for a colonoscopy. Recommended every three years.

The digital rectal exam (i.e., a procedure whereby the doctor feels the lower rectum for anything abnormal) is no longer a suggested screening method for colorectal cancer.

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Symptoms and Diagnosis

Because colon and rectal cancers can produce few, if any, symptoms in their early stages, many people don’t know anything is wrong until the disease has reached its later stages. As advanced-stage cancer is often difficult to cure, palliative treatment options may become the primary course of treatment.

Symptoms (or signs) of colon cancer include:

  • Bloody or dark-colored stool
  • Chronic abdominal pain
  • Chronic gas, constipation, or diarrhea
  • Continuously fluctuating bowel movements
  • Fatigue
  • Feeling that bowel won’t empty completely
  • Rectal bleeding
  • Unexplained weight loss
  • Weakness

The average human colon is approximately six feet long. Colon and rectal cancers begin in the inner lining of the large intestine and rectum, respectively, as small polyps. To determine if the polyps are benign (noncancerous) or malignant (cancerous), doctors typically use imaging and surgical tests. The most commonly used tests to diagnose colon cancer are colonoscopy and flexible sigmoidoscopy.

Prognosis and Treatment

In 2016, of the 136,000 people diagnosed with colorectal cancer, over 50,000 died of the disease. Each prognosis depends on the type of colorectal cancer (adenocarcinoma, signet ring, mucinous, carcinoid), the stage of cancer, and the overall health of the patient.

Adenocarcinomas are, by far, the most common type of colon and rectal cancers, accounting for 96 percent of all cases. Some adenocarcinoma subtypes have worse prognoses (such as signet ring and mucinous) though, if diagnosed early enough, colon cancer may be curable via surgery, chemotherapy, radiation, or a combination of several procedures. The spread of tumors to other organs and metastases to lymph nodes, however, may indicate only palliative treatment options.


As diagnostic and treatment methods for colon and rectal cancers have improved – putting the number of colon cancer survivors over one million in the U.S. – incidences of colorectal cancers have increased among people under the age of 55. Subsequently, health experts encourage individuals in high-risk categories to practice prevention techniques to reduces their chances of getting cancer.

Lifestyle changes are the simplest to employ and include eating more fruits and vegetables, fewer red meat and processed meats, drinking in moderation or not at all, quitting smoking, exercising regularly, and maintaining a healthy weight.

Taking aspirin regularly, for patients at high risk for colorectal cancer, may reduce an individual’s risk of developing the disease, but researchers have not been able to determine the dose or length of time required to effectively reduce risk. Too, aspirin can cause ulcers and bleeding in the stomach or intestines.

If you believe you are at risk of getting colon cancer, see your doctor to discuss your personal history. They may schedule a colon cancer screening if you are in a category with a greater chance of developing cancer.

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