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Colorectal Cancer—It’s real and very common!

Colorectal cancer (CRC) affects the rectum and the colon of both men and women worldwide. It is a malignant tumor and can be a lethal disease. Colon and rectal cancer are often grouped because they have many features in common. Cancer starts when cells in the body begin to grow out of control. To learn more about how CRC start and spread, see What Is Cancer? 

This article will explore the causes, symptoms, treatment, and prevention of CRC.

How common is colorectal cancer? 

In 2019, the estimated number of new cases of CRC in Africa was 58,000 (95% uncertainty interval (UI): 52,000–65,000), with an age-standardized case of 8.7 (95% UI: 8.–9.4) per 100,000 in both sexes. In the United States, excluding skin cancers, CRC is the third most common cancer in men and women, with approximately 151,030 new cases diagnosed annually. The American Cancer Society estimates 106,970 new cases of colon cancer in 2023. Globally, country-specific incidence and mortality rates are available from the World Health Organization GLOBOCAN database. Colorectal cancer is slightly more common among men than women.


The exact cause of CRC is not known. However, researchers identified several factors that can increase risk, although it’s not yet clear the causal link between risk factors and CRC. These factors can be grouped into two main areas: inherited gene mutations and acquired gene mutations. Inherited gene mutations refer to DNA mutations passed on from parents to offspring, while acquired gene mutations occur during a person’s lifetime.

In most cases of CRC, the DNA mutations that lead to cancer are acquired rather than inherited during a person’s life. Certain risk factors probably play a role in causing these acquired mutations, but currently, it’s not known what causes most of them. However, some modifiable and non-modifiable risk factors have been linked to increased risk of CRC.

Modifiable risk factors 

  • Obesity: Being overweight or obese raises one’s risk of contracting and dying from CRC. The risk is higher in men.
  • A diet low in fiber, high in red meats, and processed meats high in fat can increase the risk of CRC. The risk of CRC can also be increased by a diet high in refined carbohydrates like fizzy drinks, white flour, white pasta, noodles, white rice, sugar-sweetened foods, sweets, and pastries.
  • Cooking meats at very high temperatures (like frying, broiling, or grilling) creates chemicals that might raise cancer risk. It’s unclear, though, how much this may increase your risk of CRC.
  • Colorectal cancer and physical activity are linked. Therefore, regularly exercising, whether moderate or intense, can lower the risk of CRC.
  • Evidence suggests that smoking increases the risk of developing CRC, and your risk rises as you smoke more cigarettes and do so for a more extended period. Conversely, smoking cessation lowers the risk of CRC.
  • Alcohol consumption has been linked to a higher risk of CRC in men and women, although the evidence is more robust in men.

Non-modifiable risk factors 

  • Inflammatory bowel disease. If you have inflammatory bowel disease, including ulcerative colitis or Crohn’s disease, your risk of CRC increases. Inflammatory bowel disease differs from irritable bowel syndrome, which does not appear to increase your risk for CRC.
  • Age. As you get older, your risk of CRC increases. Although it can occur in young individuals, it is much more typical in people over 50. The cause of the rise in CRC in individuals under 50 is still unknown.
  • Racial and ethnic background. American Indian and Alaska Native people have the highest rates of CRC in the US, followed by African American men and women. Jews of Eastern European descent (Ashkenazi Jews) have one of the highest CRC risks of any ethnic group worldwide. 
  • Type 2 diabetes. People with type 2 (usually non-insulin dependent) diabetes have an increased risk of CRC. Both type 2 diabetes and CRC share some of the same risk factors (such as being overweight and physical inactivity).


A factor with an unclear effect on colorectal cancer risk

  • Working night shifts. According to research, routinely working the night shift may increase your risk of developing rectal cancer. This may be brought on by variations in melatonin levels, a hormone affected by light changes. More research is required in this area.


According to Mayo Clinic, the signs and symptoms of colon cancer include:

  • Persistent change in your bowel habits, including diarrhea or constipation, or a change in the consistency of your stool.
  • Rectal bleeding or blood in your stool.
  • Persistent abdominal discomforts, such as cramps, gas, or pain.
  • A feeling that your bowel doesn’t empty completely
  • Weakness or fatigue
  • Unexplained weight loss
  • Many people with colon cancer may experience no symptoms in the early stages of the disease. Symptoms will likely vary depending on the cancer’s size and location in your large intestine.


It is recommended that average-risk patients over 45 years be screened for CRC. It is, however, interesting to note that there are occasionally some harms of screening for CRC related to the risks from colonoscopy, including perforation.

A few essential questions can help to gauge a patient’s risk of CRC. These include:

  • Have you ever had CRC or an adenomatous polyp?
  • Have any biological family members had CRC or a documented advanced polyp?
  • Do you have inflammatory bowel disease?
  • Did you receive abdominal radiation for childhood cancer?


Colorectal cancer is diagnosed after the onset of symptoms which include:

  • Screening colonoscopy
  • Non-invasive stool-based testing such as fecal occult blood testing via fecal immunochemical test or guaiac fecal occult blood test in most patients.
  • CT colonography if indicated.


Treatment is with surgical resection, sometimes combined with chemotherapy and/or radiation. However, it should be noted that the treatment outcome varies widely depending on the stage of the disease.

  • Surgery: Surgery for curing CRC can be attempted in 70% of patients presenting without metastatic disease. This consists of wide tumor resection with re-anastomosis of bowel segments.
  • Chemotherapy: This improves the survival of CRC patients. Some newer drugs used individually or in combination include capecitabine, irinotecan, and oxaliplatin. Monoclonal antibodies such as bevacizumab, panitumumab, and cetuximab are also being used with some effectiveness.
  • Radiation

Reducing the risk of CRC

There is evidence that diet, weight, and exercise are strongly linked to CRC risk, and lifestyle changes can also lower the risk. The following steps can be taken to reduce your risk of CRC.

  • Get screened, especially if you are older than age 45 years. Screening can find and remove polyps that are precancerous growths.  
  • Increase the fiber in your diet by eating lots of vegetables, fruits, and whole grains. 
  • Regularly exercise and maintain a healthy weight.
  • Quit smoking if you are a smoker. 
  • Avoid alcohol because it has been linked to a higher risk of CRC.

Bottom line

Colorectal cancer contributes immensely to the loss of lives annually. However, most of its risk factors are modifiable. Thus, healthy lifestyle modifications will help reduce the morbidity and mortality of CRC. Moreover, continuous education is essential to raising awareness about CRC to save lives, especially in Africa, where many individuals are unaware of the disease. Individuals increase their chances of survival by being aware and taking the necessary precautions to prevent and detect CRC early.

Resources for your patients

National Cancer Institute CRC – Patient Version

American Cancer Society Colorectal Cancer

UPMC Hilman Cancer Center Colorectal & GI Cancer Patient Education & Resources

Following the Ministry of Health guidelines in your local setting is advised where available.

Godswill Boni, PharmD, is a multi-talented pharmacist who loves health blogging and medical writing. You can reach him here.  

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