Colon cancer: Causes, risk factors and symptoms

Colorectal cancer is cancer that starts in the lining of the large intestine (colon) or the rectum (end of the colon). The cause is unknown, but benign polyps often develop into cancer. In addition, some risk factors are known for developing colorectal cancer. The doctor usually performs a colonoscopy and biopsy to be sure of the diagnosis. The treatment consists of surgery to remove (part of) the colon, in combination with chemotherapy and/or radiotherapy. Early diagnosis often leads to a complete cure.

  • Synonyms colon cancer
  • Epidemiology colorectal carcinoma
  • Causes of colorectal cancer
  • Risk factors in colorectal cancer
  • Cancer runs in families
  • Symptoms
  • Diagnosis and examinations: Inspection of the colon
  • Treatment and prognosis
  • Succession
  • Prevention and screening through diet, FOBT test and colonoscopy
  • Complications

Synonyms colon cancer

Colon cancer is known in medical terms as:

  • colon carcinoma
  • colorectal carcinoma
  • colorectal cancer
  • colon cancer

Epidemiology colorectal carcinoma

Colorectal cancer is the third most common cancer worldwide and also in the Netherlands. The prevalence per 100,000 (at all ages) is 53.5 for men and 36.7 for women. The incidence increases with age. In the Netherlands, approximately 13,000 new patients are diagnosed with colon cancer every year. In Belgium, this number is approximately 9,000 patients who are diagnosed with colorectal cancer every year. The average age at diagnosis is 60-65 years. About 20% of patients already have metastases at diagnosis. The disease is much more common in Western countries than in Asia or Africa.

Causes of colorectal cancer

Most colorectal cancers develop as a result of a stepwise progression from normal mucosal adenoma (usually benign glandular tissue growth of the mucous membrane) to an invasive cancer. This progression occurs as a result of an accumulation of abnormalities in a number of critical growth-regulating genes. This process, known as the adenoma-carcinoma sequence, describes the development of colon cancer from the normal intestinal mucosa through various stages of polyps with increasingly serious abnormal cells and tissues.

Risk factors in colorectal cancer

Increased risk

Some conditions and medical treatments as well as environmental factors increase the risk of colorectal cancer.

Conditions and medical treatments
The following conditions and medical treatments are a risk factor:

  • abdominal radiotherapy (treatment via radiation to the abdominal area)
  • acromegaly (enlargement of body extremities due to an excess of growth hormones (after puberty))
  • ulcerative colitis (chronic intestinal disease with diarrhea, chronic abdominal pain and painful bowel movements)
  • intestinal polyps (benign growths, sometimes a precursor to cancer)
  • Crohn’s disease (condition with abdominal pain, diarrhea and weight loss)
  • family history of colon cancer
  • long-term ulcerative colitis
  • Papillomas (benign epithelial growths with nipple-like elevations
  • personal history of breast cancer
  • diabetes mellitus
  • ureterosigmoidostomy (surgical connection between ureter and s-shaped part of the large intestine)

Alcohol abuse is a possible risk factor for colon cancer / Source: Jarmoluk, Pixabay

Environmental factors
Some environmental factors also play a role in the development of colorectal carcinoma (cancer on the skin, mucous membranes and organs):

  • alcohol abuse
  • the consumption of red and processed meat
  • animal fat (saturated)
  • an increasing age
  • a diet low in dietary fiber; fiber increases feces and reduces travel time
  • physical inactivity
  • obesity (body and abdomen)
  • older than sixty years
  • smoking
  • sugar consumption
  • of African American or European descent

Reduced risk

  • aspirin and other NSAIDs (non-steroidal anti-inflammatory drugs)
  • consumption of vegetables, garlic, milk, calcium
  • combined estrogen/progesterone hormone replacement therapy (replacement therapy)
  • exercise (only a smaller risk for cancer in the colon itself, so not for rectal cancer))
  • increased dietary fiber intake

Cancer runs in families

A family history of colorectal cancer puts family members at increased risk. A family history is the most common risk factor for colorectal cancer, besides age. Familial adenomatous polyposis (condition characterized by more than a hundred adenomatous polyps) is the most recognized predisposing syndrome for colorectal cancer, but accounts for less than 1% of all colorectal cancers. Polyps are benign stalk-shaped growths of the lining of the large intestine. HNPCC (hereditary, non-polyposis, colorectal carcinoma) accounts for 3-10% of hereditary cancers. In addition, some colon cancers are (partly) caused by a hereditary predisposition (familial risk). An estimated 10% to 30% of all colon cancers are hereditary. However, most colon cancers are sporadic and occur in individuals without a strong family history.


Symptoms of colon cancer include altered bowel habits (diarrhea, constipation) with looser and more frequent bowel movements, rectal bleeding, painful bowel movements (tenesmen), weight loss and symptoms of anemia. Loose and frequent stools, with or without abdominal pain (in the lower abdomen), are common symptoms of left-sided colon injuries. Rectal and sigmoid cancer (sigmoid: S-shaped part of the large intestine) often cause black stools (feces that are mixed with blood) and blood loss through the anus. Hard stools are not a risk factor for colon cancer. Cancers present in the cecum and right colon are often asymptomatic until the patient presents with ferric anemia (anemia due to iron deficiency). Colon cancer may present with intestinal obstruction (a blockage in the intestines). Occasionally, ascites (fluid accumulation in the abdomen) also occurs.

Diagnosis and examinations: Inspection of the colon

Physical examination

Sometimes the doctor will feel a rectal or abdominal mass. With metastases in the liver, an enlargement of the liver (hepatomegaly) is possible.

Diagnostic research

Patients over 35-40 years of age who develop new large bowel complaints require a thorough examination annually.

A digital inspection of the rectum is essential, which is why the doctor always performs a sigmoidoscopy.

Colonoscopy and biopsy
Furthermore, a colonoscopy (colonoscopy: internal examination of the colon) is the gold standard for detecting colon cancer. The doctor performs a biopsy (removing a piece of tissue and having it examined microscopically).

CT scan or barium enema
A double-contrast barium enema also visualizes the colon, but the doctor often uses a CT scan to visualize the colon. A CT scan of the chest, abdomen and pelvis is also necessary to evaluate the tumor size, local spread and metastases in the liver (liver metastases) and lungs (lung metastases).

Ultrasound and MRI scan
For rectal cancer, the doctor uses an endoanal ultrasound and an MRI scan of the pelvic area. An MRI scan is also useful to identify other suspicious lesions (obtained through other imaging tests).

PET scan
A PET scan is necessary to detect occult metastases and to check suspicious lesions.

Fecal occult blood test
A fecal occult blood test (FOBT) is used as a mass screening instrument, but has no value in the hospital or general practice. This examination reveals the presence of small amounts of blood in the stool.

Differential diagnosis

The doctor uses many tests to rule out other conditions before diagnosing colon cancer:

  • Crohn’s disease
  • diverticulosis (formation of bulging sacs or blisters (diverticula) on the intestinal wall)
  • ulcerative colitis
  • ileus (stopped bowel movements with blockage of intestines)

Treatment and prognosis

About 80% of patients with colon cancer undergo surgery in which the doctor removes (part of) the colon, although only half of them survive for another five years. The surgical treatment depends on the type of cancer. Long-term survival depends on the stage of the primary tumor and the presence of metastases. Long-term survival rates are good when the cancer is completely removed surgically with sufficiently wide margins and regional lymph node clearance. This operation is done in combination with pre- or postoperative radiotherapy and/or chemotherapy.


All patients who have undergone surgery receive a total colonoscopy before surgery to detect any additional lesions. In addition, some patients require regular colonoscopy. A CT scan is required up to five years after surgery to identify liver metastases

Prevention and screening through diet, FOBT test and colonoscopy

Power supply

A low-fat and high-fiber diet is recommended for prevention for patients at risk with a strong family history and hereditary syndromes, such as FAP (familial adenomatous polyposis) and HNPCC (hereditary, non-polyposis, colorectal carcinoma).

FOBT test

An FOBT test is a screening tool for colorectal cancer. Several large randomized studies have shown a reduction in cancer-related mortality of 15-33%. The disadvantage of this screening element is its relatively low sensitivity, which means that many patients receive a negative colonoscopy.


A colonoscopy is the gold standard for internal examination of the colon and rectum and is the examination instrument for high-risk patients. Furthermore, doctors are increasingly using CT colonography (virtual colonoscopy).


Complications of colon cancer include:

  • a blockage of the large intestine, causing an intestinal obstruction
  • development of a second primary colorectal cancer
  • recurrent colon cancer
  • spread of cancer to other organs or tissues, such as brain metastases (spread to the brain)

read more

  • Colonoscopy: Tips to facilitate the examination
  • Cancer pain: Causes & types of pain and types of pain medication
  • Cancer Treatment: Different treatments for cancer
  • Cancer recurrence (recurrence): Types, risk factors and tips
  • Lynch syndrome: Increased risk of colon cancer
Colon cancer: Causes, risk factors and symptoms
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