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Colon Cancer early symptoms, risk factors, treatment – Colon Cancer

Colon cancer is a type of cancer that primarily affects older people. It involves the digestive tract’s large bowel (colon).

There is a slow decline in the appearance of new colon cancer cases within the population. Nonetheless, it remains the third most common cancer. Approximately there are over 1.850.000 new cases each year and over 650.000 deaths per year worldwide.

In this article, the reader will find explanations to some of the most customary and not so customary questions on this disease. There will be questions like what the stages are, how does it start, and many more. Also, there is a brief explanation of basic concepts for a better understanding of the topic.

By reading this article, you will acquire significant insights about colon cancer, its symptoms, causes, meaning, complications, and many more. Consequently, please stay reading this article to learn essential information on this specific topic directly from a doctor.  

How does colon cancer start?

There is no simple answer for this, as doctors and scientists do not explicitly know what causes colon or colorectal cancer. Most of the cases begin with an alteration in the DNA of healthy cells. That means that these cells go through a process of mutation. The activity of the cell changes permanently if the DNA changes. The DNA is the one that carries the instructions that tell the cell what to do. 

Usually, the cells grow and divide in an orderly way to keep the body functioning normally. But after there is a mutation of the cells and these cells become cancerous, cells continue to divide even when there is no need for new cells. The accumulation of these cells produces tumors. The collection of genetic mutations can either be acquired through time or inherited. 

There is scientific evidence that adenomatous polyps or precancerous polyps that acquire DNA changes directly correlate to developing colon cancer. On the other hand, with proper colon cancer screening, the early detection and removal of colon polyps will reduce the risk of developing colon cancer.

What are the stages of colon cancer?

To classify all the types of cancer, doctors use an international system that receives the name of TNM. TNM system stands for Tumor (T), node (N), and Metastasis (M). Doctors use the results from diagnostic tests and scans to classify cancer powerfully. With this system, doctors look to respond to the following questions for each item.

  • Tumor (T): Did the primary tumor grow into the colon or the rectum wall? How many layers of the colon have affected?
  • Node (N): Did the tumor spread to the lymph nodes? Which ones? How many lymph nodes are affected?
  • Metastasis (M): Has cancer spread to other parts of the body? Which ones? How much?
File:Blausen 0604 LargeIntestine2.png

The results of these questions are used to determine the staging of cancer in each patient. Also, the results of each item are combined to make an assertive diagnosis. Five stages for Colon Cancer go from Stage 0 or Zero and Stages I to IV (1 to 4). The staging becomes very useful to determine the best type of treatment, considering the patient’s condition.

Stage 0

Colon cancer stage 0 receives the name of cancer in situ. The cancer cells or tumor cells are only invading the mucosa of the colon or rectum’s inner lining. There is no damage to nearby lymph nodes or other organs.

File:2421 Histology of the Large IntestineN.jpg
Histology of the Large Intestine

Stage I

Colon cancer in stage I means the growth of the tumoral cells and cancer. Cancer has grown through the mucosa, and it has begun to invade the muscle layers of the large bowel. In this stage, cancer remains in the bowel. There is no invasion or damage of nearby lymph nodes or signs of metastasis.

Stage II

Starting from this stage, things get a little bit difficult. It will depend on the combination of results of the TNM. Nonetheless, cancer does not reach nearby lymph nodes or other organs. It will classify the overall growth of the Tumor and its implications within the body. The staging will divide into three different types. 

  • II A: For stage II-A, cancer grows through the entire wall of the colon or the rectum. 
  • II B: In stage II B cancer, asides from growing through the entire wall of the colon, it grows as well through the lining of the abdomen or the visceral peritoneum. The visceral peritoneum is a thin layer that covers all the organs within the abdomen.
  • II C: Stage II C refers to the most troublesome type of stage II cancer colon. The tumor grows through the entirety of the colon and visceral peritoneum, and it begins to grow into nearby structures or organs. 

Stage III

For Stage III, there are different types as well as Stage II, with the difference that each type subdivides itself into other groups depending on the damage. When the doctor talks about Stage III bowel cancer, there is already an invasion of the lymph nodes. The staging of the primary tumor may vary. However, in Stage III, there is no presence of metastasis (distant organ involvement) yet. The classification for Stage III is the following.


  • Group I: On Group I of the patients with Stage III cancer, the tumor invades the superficial layers or the colon’s muscle layers. Nonetheless, cancer has spread to 1 to 3 lymph nodes.
  • Group II: Group II of the Stage III cancer has a slight difference from the previous one. The tumor invades only the colon’s mucosal layer, but it has invaded from 4 to 6 nearby lymph nodes.


  • Group I: On Group I of the patients with Stage III B cancer, the tumor may invade the whole colon through all of its layers, or it can even invade the visceral peritoneum. It invades as well from 1 to 3 lymph nodes.
  • Group II: For Group II, the tumor does not invade as much as in Group I. The tumor’s reach goes as much as the muscular layers or through the whole colon, and it does not reach the visceral peritoneum. However, there is an invasion of 4 to 6 lymph nodes. 
  • Group III: On Group III, the tumoral growth is even lower. The tumor may invade the mucosal layer of the colon or as much as the muscle layers. Nonetheless, there is damage in 7 or more lymph nodes.


  • Group I. The tumor may invade the whole wall of the colon and the visceral peritoneum, with affection from 4 to 6 lymph nodes.
  • Group II. The primary tumor remains the same as the group I but with the difference that there is the affection of 7 or more lymph nodes.
  • Patients in group III have an invasion of other tissues asides from the colon as the primary tumor outgrows the wall and invades nearby tissues. On the other hand, patients on Group III have the affection of 1 to 3 lymph nodes.

Stage IV

This is the final stage of Colon Cancer; for this stage, cancer already has metastasis. That means that the abnormal cells or cancerous cells have spread through the body. Cancer cells can reach nearby organs like the liver, small intestine, stomach, and many more. Stage IV also has three types, but with the difference in these classifications, it does not matter the tumor’s size and how many lymph nodes are affected. The classification is the following.

  • A IV: Cancer has already spread, and it has invaded one part of the body or one organ of the body like lungs or liver.
  • B IV: Almost the same as IV A but with the difference that cancer has spread to more than one organ within the body.
  • C IV: Cancer invades the whole peritoneum and as well invades other organs or parts of the body.

What are the signs and symptoms of colon cancer?

Colon cancer symptoms are not very specific as they are very general or common to other diseases. Many of these symptoms may have a cause that does not involve cancer. Among the possible causes are infections, hemorrhoids, or inflammatory bowel disease. Nonetheless, having any of these symptoms should be more than enough reason to visit a doctor.

Among the most common symptoms are the following:

  • Changes in bowel habits: This includes diarrhea, constipation, or narrowing of the stool.
  • Rectal bleeding
  • Dark stools or blood in the stool
  • Weakness
  • Fatigue
  • Weight loss without explanation
  • Persistent abdominal discomforts like cramping, gas, or pain
  • A feeling that the bowel does not empty completely after evacuating

If the cause is colon cancer, this is mainly because cancer has already grown or spread. Symptoms do not commonly appear in the early stages of the disease. That is why it is important to get colorectal cancer screening to prevent disease development and remove the precancerous growths known as polyps. Cancer prevention is one of the most effective ways to avoid this disease.

At what stage does colon cancer show symptoms?

There is not an exact stage at which colon cancer starts to show symptoms. This really depends on the patient, the location, and the size of the tumor. In fact, only around 50% of people will develop actually recognizable symptoms of colon cancer. However, most patients will get symptoms at stage 3 of the disease. This is because, at stage 3, cancer has spread beyond the colon to nearby lymph nodes. Also, most symptoms at stages 1 and 2 can go unnoticed or simply be absent. 

One of the most important symptoms for suspecting colon cancer is rectal bleeding. However, the bleeding at early stages can be present but invisible and can only be confirmed through testing. The most common symptoms for stage 3 colon cancer include narrow stools, rectal bleeding or blood in your stools, and abdominal pain. Since colon cancer symptoms take time to appear, cancer can be advanced by the time you suffer symptoms. If you happen to experience these symptoms, you shouldn’t wait any longer and get medical help.

What are the risk factors for developing colon cancer?

Risk factors are anything that may raise the probability of getting a disease or a condition, in this specific case, colon cancer. Nonetheless, having one or several risk factors does not mean that the person will get the disease. On the other hand, there are patients with no risk factors that may develop the disease. There are two types of risk factors for this disease, the ones that the patient can change and the ones that are not modifiable. There will be a list for both of them.

Modifiable Risk Factors

  • Obesity: People who suffer from overweight tend to have an increased risk of developing colon cancer and dying from it compared to people who have normal weight.
  • Sedentary Lifestyle: Being physically inactive increases the risk of developing colon cancer. A person who regularly does physical activity has a lower cancer risk.
  • Diet: There is a direct correlation between food and the risk of developing colorectal cancer. People who have diets high in red meats and processed meats have a higher risk. Also, having Vitamin D deficiency increases the risk for these patients.
  • Smoking: It is worldwide known that tobacco has a direct correlation with developing lung cancer. But tobacco has links to other types of cancer as well as colon cancer. Smoking can increase the risk of developing this disease.
  • Alcohol Use: Alcohol abuse is heavily linked to the development of colorectal cancer. Light to moderate alcohol intake has a certain type of risk. The recommendation is that people should not have more than two drinks a day for men and one drink a day for women.

Non-Modifiable Risk Factors

  • Older Age: Getting older means that the risk of developing colon cancer increases. Most of the cases for this disease happen to patients over 50 years old. So as the age goes up, the risk goes up as well. Although nowadays some people are developing colon cancer even younger than forty years.
  • Personal History: Patients with a history of colorectal polyps or colorectal cancer are at higher risk than the rest of the population. If the polyps are large or if there are many of them, the colorectal cancer risk increases. Even if it was removed completely, people with colorectal cancer are at higher risk of developing new cancers.
  • Inflammatory Bowel Disease: People who suffer either from ulcerative colitis or Crohn’s disease have a higher colon cancer risk. This is a condition in which the colon suffers from inflammation constantly. If left untreated, the lining of the colon may suffer from dysplasia (pre-cancerous lesions).
  • Diabetes: People with Type 2 Diabetes are at higher risk of developing Colon Cancer. Especially because they also share some of the risk factors like obesity and a sedentary lifestyle.
  • Familiar History: Most colon cancer cases occur in people without familiar history, but this does not exclude this risk factor. The truth is that 1 out of 3 people who develop colon cancer have a familiar who suffered from this disease. Colon cancer risk increases if there is someone in your family with this condition, especially if they are first degree relatives like parents or siblings.
  • Inherited Syndromes: A small percentage of patients develop colon cancer due to gene mutations that run in the family. The most common types of syndromes that can cause colorectal cancer are Familial Adenomatous Polyps (FAP) and Lynch Syndrome.
  • Radiation Therapy: Previous treatments of radiation for other types of cancer in the abdomen may increase the risk of developing colon cancer.

When should someone seek medical care for suspected colon cancer?

One of the most important aspects of the prevention and diagnosis of colon cancer is screening. Doctors recommend screening tests for colon cancer, even for healthy patients with no colon cancer symptoms. These screenings are especially recommended in patients over 50 years old and patients with a higher risk of developing colon cancer.

The reason for annual screenings is that finding colon cancer in its early stages gives a greater chance for cure. The earlier the diagnosis, the more chances you have of surviving this condition. The screening usually includes blood tests and imaging studies like a colonoscopy. In fact, with a colonoscopy, your doctor can remove lesions like polyps before they turn into cancer.

On the other side, if you are experiencing gastrointestinal symptoms, you should see your doctor. Remember that, at the early stages, colon cancer can show some unspecific symptoms that can be mistaken for less serious conditions.

Common symptoms for colon cancer include rectal bleeding, change in bowel pattern, changes in shape or size of stools, and unexplained weight loss. Colon cancer can also cause fewer alarming symptoms like fatigue, changes in appetite, and bloating. Make an appointment with your doctor if you have any of these symptoms for more than two weeks. 

Can a blood test detect colon cancer?

This can be a tricky question as a simple blood test may not indicate the presence of colon cancer. Doctors often ask for these tests to check the patient’s overall health and determine if there is damage to other organs. On the other hand, specific tests may indicate if there is abnormal or cancerous activity. Your doctor may ask for tumor markers within the blood. The most common type of tumor marker for Colon Cancer is the Carcinoembryonic Antigen or CEA.

It is important to know that this test does not make a diagnosis by itself. Doctors need to correlate the signs and symptoms of the patient with these results. This is mainly because these tumor markers can be abnormal for other reasons than cancer. They do not always appear on patients who have colorectal cancer.

What exams and tests diagnose colon cancer?

To determine if the patient has colon cancer, people should first get an interview with his or her doctor to analyze the case. Many of the patients may have a familiar history or personal history that may not seem relevant to them but can help the doctor.

Doctors generally recommend people to start colon cancer screening at age 50 as the risk increases from that age. There are several options for screening, which leads us to the next point. Your doctor will ask for a series of tests divided into two types, invasive and non-invasive. The tests are the following:

Non-Invasive Tests

These tests are based on the stool study; they do not need any type of preparation like special diets or bowel preparation. Nonetheless, if the result shows any abnormalities, your doctor may recommend an invasive test.

  • Fecal Immunochemical Test (FIT): Alongside the “guaiac-based fecal occult blood test (gFOBT),” they are used to determine if there is the presence of tiny amounts of blood in the stool. These findings may be a sign of colon cancer or developing polyps. The downside is that these tests cannot tell where the blood is coming from. 
  • Stool DNA Testing: It is a test that also analyzes the stool but looking for certain DNA or gene changes. This may be an early indicator that there is the presence of pre-cancerous growths and cancer cells.

Invasive/Visual Tests

  • Colonoscopy: This test consists of a thin tube that goes through the anus enabling the doctor to see inside the colon. The doctor will also take samples of the tissue for further analysis and rule out certain conditions.
  • Flexible Sigmoidoscopy: It is very similar to colonoscopy; the only difference is that the tube is flexible. This enables the doctor to see the rectum and the sigmoid colon. It is very useful to see the final portion of the gastrointestinal tract.
  • Biopsy: Through both of the previous tests, doctors may take a portion of your bowel for further tests and analysis. This will allow them to determine if there is a presence of cancerous cells within the tissue.
File:Diagram showing a colonoscopy CRUK 060.svg
Diagram showing a colonoscopy

What are the treatment options for Colon Cancer?

There are many different types of colon cancer treatment; however, they will depend on the patient’s situation. Doctors consider the location of cancer, the overall health status of the patient, and the extension of cancer. Among the most common types of cancer treatment are the following:

  • Colon Cancer Surgery for Early Stages: This will be an option if the cancer is very small. Your doctor may remove the cancerous cells or polyps through different methods. Among the methods is colonoscopy, which can also be used for treatment asides from diagnosis, endoscopic mucosal resection, and laparoscopic surgery. 
  • Colon Cancer Surgery for Advanced Stages: When the tumor grows too much that resection cannot be minimally invasive, your doctor may recommend these methods. Among the types of surgery is the partial colectomy. The doctor removes the part of the colon with cancer. Also, there are options like lymph node removal. If there is no possibility to reconnect healthy portions of the colon, your doctor may perform an ostomy. This will allow your body to eliminate feces. An ostomy is creating a hole in the abdominal wall (your belly) that connects to a bag for defecating.
  • Chemotherapy: This therapy uses drugs that destroy cancer cells anywhere in the body. These drugs destroy any rapidly growing cell, which means it can attack either cancerous or healthy cells. To perform this treatment, patients generally do not need to stay in the hospital. 
  • Targeted Therapy: It is a type of treatment that focuses on specific abnormalities of the cancer cells. It is designed to attack specific proteins within the cells. If a cell is producing too much of it, the therapy will focus on that cell, sparing the healthy ones.

Do you have symptoms of colon cancer?

This tool is a Colon Cancer Symptoms Checker. It gathers the most important signs, symptoms, and risk factors for this cancer. Therefore, the tool will tell anybody who uses it the likelihood of their symptoms because of colon cancer. Also, the tool will determine people with risk factors or needing screening for it. Using the tool is free and would only take a few minutes.

What do you think?

Written by Dr. Esteban Kosak

Doctor of Medicine - MD Recently Graduated from Medical School and inspired to aid the global population during this situation. I think that we shall no longer be waiting to see a doctor when we feel sick. Several times we feel disease searches in Google drive us to a rabbit hole and come out thinking that we may die of cancer or something very serious, given that symptoms may seem to fit a wide variety of illnesses. Since I recently graduated from medical school. I have all the medical information fresh in my mind. My thorough experience as an expert researcher allows me to very-well known the different diseases and conditions that affect human bodies. Empowered by the United Nations 17 Sustainable Development Goals (SGDs). I think that we all can provide a grain of sand to help humanity. That's why we created Symptoms.Care a place where you can come and screen your symptoms and find what different illnesses can be related to them. Armed with the right information you can instantly, discretely, secure and from the comfort of your home talk with a Doctor that can Evaluate your Symptoms and help you seek the right treatment.


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