Colorectal Cancer: Causes, Symptoms and Treatments

Colorectal cancer, also known as bowel cancer, colon cancer or rectal cancer, is any cancer (a growth, lump, tumor) of the colon and the rectum. The World Health Organization and CDC say it is the second most common cancer worldwide, after lung cancer.

The American Cancer Society suggests that about 1 in 20 people in the US will develop colorectal cancer during their lifetime, with the risk being slightly higher for men than for women. Due to advances in screening techniques and improvements in treatments, the death rate from colorectal cancer has been dropping for over 20 years.

A colorectal cancer may be benign or malignant. Benign means the tumor will not spread, while a malignant tumor consists of cells that can spread to other parts of the body and damage them.

The colon and rectum

Anatomy of the large intestine
The large intestine is also called the colon or large bowel.

The colon and rectum belong to our body’s digestive system – together they are also known as the large bowel.

The colon reabsorbs large quantities of water and nutrients from undigested food products as they pass along it.

The rectum is at the end of the colon and stores feces (stools, waste material) before being expelled from the body.

Symptoms of colorectal cancer

  • Going to the toilet more often.
  • Diarrhea.
  • Constipation.
  • A feeling that the bowel does not empty properly after a bowel movement.
  • Blood in feces (stools).
  • Pains in the abdomen.
  • Bloating in the abdomen.
  • A feeling of fullness in the abdomen (maybe even after not eating for a while).
  • Vomiting.
  • Fatigue (tiredness).
  • Inexplicable weight loss.
  • A lump in the tummy or a lump in the back passage felt by your doctor.
  • Unexplained iron deficiency in men, or in women after the menopause.

As most of these symptoms may also indicate other possible conditions, it is important that the patient sees a doctor for a proper diagnosis. Anybody who experiences some of these symptoms for four weeks should see their doctor.

Causes of colorectal cancer

Experts say we are not completely sure why colorectal cancer develops in some people and not in others. However, several risk factors have been identified over the years – a risk factor is something which may increase a person’s chances of developing a disease or condition.

The possible risk factors for colorectal factors are:

  • Being elderly – the older you are the higher the risk is.
  • A diet that is very high in animal protein.
  • A diet that is very high in saturated fats.
  • A diet that is very low in dietary fiber.
  • A diet that is very high in calories.
  • A diet that is very high in alcohol consumption.
  • Women who have had breast, ovary and uterus cancers.
  • A family history of colorectal cancer.
  • Patients with ulcerative colitis.
  • Being overweight/obese.
  • Smoking. This study found that smoking is significantly associated with an increased risk for colorectal cancer and death.
  • Being physically inactive.
  • Presence of polyps in the colon/rectum. Untreated polyps may eventually become cancerous.
  • Having Crohn’s disease or Irritable Bowel Disease have a higher risk of developing colorectal cancer.

Most colon cancers develop within polyps (adenoma). These are often found inside the bowel wall.

How common is colorectal cancer?

Diagram of colon cancer

According to WHO (World Health Organization) colorectal cancer is the second most common tumor among both men and women (after lung tumors).

Approximately 2% of over 50-year-olds will eventually develop colorectal cancer in Western Europe.

40% of people who are diagnosed with colorectal cancer are already at an advanced stage of the cancer. For these patients surgery is probably the most likely option.

Colorectal cancer tends to affect men and women equally. However, men tend to develop it at a younger age.

Tests and Diagnosis for colorectal cancer

Screening can detect polyps before they become cancerous, as well as detecting colon cancer during its early stages when the chances of a cure are much higher. The following are the most common screening and diagnostic procedures for colorectal cancer:

Fecal occult blood test (blood stool test)

This checks a sample of the patient’s stool (feces) for the presence of blood. This can be done at the GP’s (general practitioner’s, primary care physician’s) office. However, most patients are given a kit that explains how to take the sample at home. The patient then returns the sample to the doctor’s office, and it is sent to a laboratory.

A blood stool test is not 100% accurate – it might not detect all cancers because not all of them bleed. Even cancers that do bleed often do not do so all the time. Therefore, it is possible that a patient has a negative result, even though he/she has cancer. Even if blood is detected, this may be caused by other illnesses or conditions, such as hemorrhoids. Some foods may suggest blood in the colon, when in fact, none was present.

Stool DNA test

This test analyzes several DNA markers that colon cancers or precancerous polyps cells shed into the stool. Patients may be given a kit with instructions on how to collect a stool sample at home. This has to be brought back to the doctor’s office, and is then sent to a laboratory.

This test is much more accurate for detecting colon cancer than polyps. However, it cannot detect all DNA mutations which may indicate that a tumor is present.

Flexible sigmoidoscopy

The doctor uses a sigmoidoscope, a flexible, slender and lighted tube, to examine the patient’s rectum and sigmoid (the sigmoid colon is the last of the colon, before the rectum). The test does not generally take more than a few minutes and is not painful; but might be uncomfortable. There is a small risk of perforation of the colon wall. If the doctor detects a polyps or colon cancer he/she will then carry on a colonoscopy to examine the entire colon and take out any polyps that are present – they will then be examined under a microscope.

A sigmoidoscopy will only detect polyps or cancer present at the end third of the colon and the rectum. If there are any in any other parts of the digestive tract it will not detect them.

Barium enema X-ray

Barium is a contrast dye that is placed into the patient’s bowel in an enema form – it shows up on an X-ray. In a double-contrast barium enema air is added as well. The barium fills and coats the lining of the bowel, creating a clear image of the rectum, colon, and occasionally of a small part of the patient’s small intestine. This procedure is often carried out along with a flexible sigmoidoscopy to detect any small polyps the barium enema X-ray may have missed. If the barium enema X-ray detects anything abnormal, the doctor may recommend a colonoscopy.

Colonoscopy

A diagram of the colonoscopy

The doctor uses a colonoscope, which is much longer than a sigmoidoscope. A colonoscope is a long, flexible and slender tube which is attached to a video camera and monitor. The doctor can see the whole of the colon and rectum. Any polyps discovered during this exam can be removed there and then – sometimes tissue samples (biopsies) may be taken instead. Taking biopsies does not hurt.

Although colonoscopies are painless, some patients are given a mild sedative to calm them down. Prior to the exam the patient may be given a large amount of laxative fluid to clean out the colon (enemas are rarely used). Bleeding and perforation of the colon wall are possible complications, but extremely rare.

CT colonography (virtual colonoscopy)

A CT (computerized tomography) machine is used to take images of the colon. The patient needs to have a cleared colon for this exam to be effective. Even if anything abnormal is detected, the patient will then need conventional colonoscopy. A study found that CT colonography may offer patients at increased risk of colorectal cancer an alternative to colonoscopy that is less-invasive, is better-tolerated and has good diagnostic accuracy.

Ultrasound scan

Sound waves are used to help show if the cancer has spread to another part of the body.

Magnetic resonance imaging (MRI)

This gives a three-dimensional image of the bowel and may help the doctor in his/her diagnosis.

Staging the cancer

The stage of a cancer means the extent of the cancer. As soon as a colon cancer diagnosis has been made the doctor will determine its stage – this helps chose the most appropriate treatment. The stages of colon cancer are:

  • Stage 0 (Also known as Duke A stage). – the earliest stage. It is still within the mucosa (inner layer) of the colon or rectum – also called carcinoma in situ.
  • Stage I (Also known as Duke B stage). – it has grown through the inner layer of the colon or rectum, but has not yet spread beyond the wall of the rectum or colon.
  • Stage II (Also known as Duke C stage). – it has grown through or into the wall of the colon or rectum. However, it has not reached the nearby lymph nodes yet.
  • Stage III (Also known as Duke D stage). – the nearby lymph nodes have been invaded by the cancer, but it has not yet affected other parts of the body.
  • Stage IV (Also known as Duke E stage). – it has spread to other parts of the body, including other organs, such as the liver, the membrane lining the abdominal cavity, lung, or ovary.
  • Recurrent – the cancer has returned after treatment. It may come back and affect the rectum, colon, or elsewhere in the body. Scientists have found that the presence of a biomarker in regional lymph nodes is an independent predictor of disease recurrence in patients with colorectal cancer.
The stages of colon cancer

Treatments for colorectal cancer

The patient’s treatment will depend on several factors, including its size and location, the stage of the cancer, whether or not it is recurrent, and the current overall state of health of the patient. A good specialist will explain all the treatment options available to the patient. This is an opportunity for the patient to ask questions and get advice on lifestyle changes that will help recovery.

Treatment options include chemotherapy, radiotherapy, and surgery:

Surgery for colorectal cancer

This is the most common colorectal cancer treatment. The affected malignant tumors and any lymph nodes that are nearby will be removed. Surgeons remove lymph nodes because they are the first place cancers tend to spread to.

The bowel is usually sewn back together. On some occasions the rectum may need to be taken out completely – a colostomy bag is then attached for drainage. The colostomy bag collects stools and is generally placed temporarily – sometimes it may be a permanent measure if it is not possible to join up the ends of the bowel.

If the cancer is diagnosed early enough, surgery may be the only treatment necessary to cure the patient of colorectal cancer. Even if surgery does not cure the patient, it will ease the symptoms.

Chemotherapy

Chemotherapy involves using a medicine (chemical) to destroy the cancerous cells. It is commonly used for colon cancer treatment. It may be used before surgery in an attempt to shrink the tumor. A study found that patients with advanced colon cancer who receive chemotherapy and who have a family history of colorectal cancer have a significantly lower likelihood of cancer recurrence and death.

Radiotherapy

Radiotherapy uses high energy radiation beams to destroy the cancer cells, and also to prevent them from multiplying. This treatment is more commonly used for rectal cancer treatment. It may be used before surgery in an attempt to shrink the tumor.

Doctors may order both radiotherapy and chemotherapy after surgery as they can help lower the chances of recurrence.

Recovery from colorectal cancer

Malignant tumors will most probably grow and spread to other parts of the body if left untreated. The chances of a complete cure depend enormously on how early the cancer is diagnosed and treated. A patient’s recovery depends of the following factors:

  • The cancer stage when diagnosis was made.
  • Whether a hole or blockage was created in the colon by the cancer.
  • Whether the cancer has come back.
  • The patient’s general state of health.

Prevention of colorectal cancer

We can do quite a lot to lower our chances of developing colorectal cancer:

  • Regular screenings – especially if you have had colorectal cancer before, you are over 60, there is a family history of this type of cancer, you have Crohn’s disease. Some experts say screening should start after the age of 50.
  • Nutrition – make sure your diet has plenty of fiber, fruit, vegetables, and good quality carbohydrates. Keep your consumption of red meat and processed meat down to a minimum, or cut them out altogether. Switch from saturated fats to good quality fats, such as avocado, olive oil, fish oils, and nuts. However, this study found that although vegetarians have an overall lower risk of developing cancers, their risk of developing colorectal cancer is higher than meat eaters.
  • Exercise – exercise regularly. Moderate, regular exercise has been shown to have a significant impact on lowering a person’s risk of developing colorectal cancer.
  • Bodyweight – keep your bodyweight healthy. Being overweight or obese raises a person’s risk of developing many cancers, including colorectal cancer.
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