Colorectal Cancer - Public Health Notes

What is Colorectal Cancer?

Colorectal cancer, alternatively referred to as bowel cancer, colon cancer, or rectal cancer, encompasses any form of cancer that impacts the colon and rectum (Note: colon and rectum are the vital components of the digestive system).
Sometimes, the colon or rectum may develop abnormal growths known as ‘Polyps’. As time passes, certain polyps have the potential to transform into cancerous cells.
Unlike many other types of cancer, colorectal cancer can often be prevented through regular screening and is highly manageable if detected at an early stage.

Key Facts

Colorectal cancer, ranking as the third most prevalent cancer globally, saw a significant number of diagnoses in 2020, with nearly 2 million cases reported.
This form of cancer stands as the third most frequent type among men and the second most common among women.
It holds the position of being the second most common cause of cancer-related deaths, accounting for approximately 1 million fatalities each year.
Individuals with a family history of colorectal cancer face an elevated risk and should undergo screening prior to the age of 45.
Screening is available for colorectal cancer, and there are cost-effective and convenient choices for at-home screening that can help in its prevention.

Types of Colorectal Cancer

1. Adenocarcinoma

Adenocarcinoma is the most common form of colon cancer, characterized by the presence of cancerous cells that line the inner surface of the colon.

2. Carcinoid tumors

Carcinoid tumors originate from cells in the intestines that produce hormones.

3. Gastrointestinal stromal tumors (GISTs)

Gastrointestinal stromal tumors (GISTs) are a type of soft tissue sarcoma that can occur in various parts of the gastrointestinal tract, although they are uncommon in the colon.
In some cases, these tumors can also be other types of sarcoma that initiate in the blood vessels or connective tissue of the colon.

Causes of Colorectal Cancer

The exact causes of most colon cancers remain uncertain.
In general, the onset of colon cancer occurs when the DNA of healthy cells in the colon undergoes mutations.
When a cell’s DNA is damaged and becomes cancerous, the cells continue dividing even when new cells are not necessary. Over time, these cells accumulate and give rise to a tumor.
Eventually, cancer cells can expand, infiltrating and destroying nearby healthy tissue.
Moreover, cancerous cells have the ability to spread to other parts of the body, forming secondary growths (metastasis).

Risk Factors of Colorectal Cancer

The risk of developing colorectal cancer rises with age.
Other risk factors of colorectal cancer include having—
- Inflammatory bowel conditions like Crohn’s disease or ulcerative colitis.
- A history of colorectal cancer or colorectal polyps, either in the individual’s personal medical background or within their family
- Presence of genetic syndromes like familial adenomatous polyposis (FAP) or hereditary non-polyposis colorectal cancer (Lynch syndrome).
Certain lifestyle choices may also contribute to an elevated risk of colorectal cancer, which include:
- Insufficient engagement in regular physical activity.
- Consumption of a diet that lacks an adequate amount of fruits and vegetables.
- Adoption of a low-fiber and high-fat diet or a diet that is high in processed meats.
- Overweight or obesity.
- Regular consumption of alcohol.
- Use of tobacco products

High Risk Groups of Colorectal Cancer

Age 50 and above
Individuals with a personal or family history of colorectal cancer
Inflammatory bowel disease (IBD) patients
Genetic syndrome carriers (FAP or Lynch syndrome)
Individuals with sedentary lifestyles
Individuals with diets high in processed foods and red meat
Overweight or obese individuals
Smokers
Excessive alcohol consumers

Signs and Symptoms of Colorectal Cancer

Persistent alterations in their bowel movements, such as diarrhea or constipation, as well as modifications in the consistency of their stool.
Bleeding from the rectum or presence of blood in the stool
Ongoing abdominal discomfort, characterized by cramps, gas, or pain
A sensation of incomplete bowel emptying
Weakness or fatigue
Unexplained weight loss
Many individuals with colon cancer may not experience any symptoms during the initial stages of the disease.
When symptoms do manifest, they can vary depending on the size and location of the cancer within the large intestine.

Fatality Rate of Colon Cancer

The five-year relative survival rate for colon cancer stands at 64.4%.
This indicates that out of every 100 individuals diagnosed with colon cancer, approximately 64 of them are projected to survive for at least five years following their diagnosis.
As for rectal cancer, its five-year relative survival rate is 67%.
This means that around 67 out of 100 people diagnosed with rectal cancer are expected to be alive after five years from the time of diagnosis.

Stages of Colorectal Cancer

Stage 0

Stage 0 of colorectal cancer, also known as carcinoma in situ, refers to the presence of abnormal or precancerous cells in the innermost layer of the colon wall

Stage I

In Stage I, the cancer has grown into the wall of the intestine but has not extended beyond the muscular layer or reached nearby lymph nodes.

Stage II

During Stage II, the cancer has progressed further into the intestinal wall but has not yet spread to adjacent lymph nodes.

Stage III

Stage III signifies that the colon cancer has spread to the lymph nodes.

Stage IV

Finally, in Stage IV, the cancer has metastasized to other parts of the body, such as the liver, lungs, or ovaries.

Screening of Colorectal Cancer

1. Colonoscopy

A comprehensive procedure that allows doctors to examine the entire colon using a flexible tube with a camera.
It is considered the gold standard for colorectal cancer screening.

2. Fecal Immunochemical Test (FIT)

A non-invasive test that detects hidden blood in the stool, indicating possible colorectal cancer.
It involves collecting a stool sample at home and sending it to a laboratory for analysis.

3. Flexible Sigmoidoscopy

Similar to a colonoscopy, but it examines only the lower part of the colon.
It involves a flexible tube with a camera being inserted into the rectum.

4. Stool DNA Test

This test analyzes DNA changes in the stool to identify potential colorectal cancer or precancerous polyps.

5. Virtual Colonoscopy (CT Colonography)

A less invasive option that uses X-rays and computer technology to create detailed images of the colon, helping to identify abnormalities.

Diagnosis of Colorectal Cancer

1. Biopsy

A sample of tissue is collected from the colon or rectum during a colonoscopy or sigmoidoscopy.
The tissue is then examined under a microscope to determine if cancer cells are present.

2. Imaging tests

These tests, such as CT scans, MRI scans, and PET scans, are used to visualize the colon, rectum, and other organs to determine the extent of cancer and if it has spread to other areas of the body.

3. Blood tests

Certain blood tests, such as the carcinoembryonic antigen (CEA) test, can help monitor the progression of colorectal cancer and assess treatment response.

Prevention of Colorectal Cancer

A key strategy for cancer prevention is to include a diverse selection of fruits, vegetables, and whole grains in your diet.
Moderation of alcohol is crucial,
Quitting smoking is a vital step.
Engaging in regular exercise is a fundamental aspect of a healthy lifestyle, and it can also contribute to cancer prevention.
Maintaining a healthy weight

Treatment of Colorectal Cancer

1. Polypectomy

This surgical procedure involves the removal of cancerous polyps.

2. Partial colectomy

Also known as colon resection surgery, this operation entails the removal of the colon section containing the tumor along with some surrounding healthy tissue.
Subsequently, surgeons reconnect the healthy sections of the colon through a procedure called anastomosis.