Colon Cancer – Risk Factors, Symptoms, Investigations, Staging, Treatment


colon cancer

How a Patient with Colon Cancer Presents?

To better understand colon cancer symptoms, watch the video below in which CancerBro meets Mr Collin, a colon cancer patient. 

To understand the disease better, we will meet Mr. Colin today, who has recently been diagnosed with colon cancer. He is Mr. Colin, who lives with his wife. For last few days, he was having abdominal discomfort and pain, and had also lost weight. Recently, he started having difficulty in passing stools, which was increasing progressively. So one fine day, he consulted doctor and underwent some investigations. Unfortunately, he was diagnosed to have colon cancer and was admitted to hospital for treatment.

CancerBro: Hi Mr. Colin, how are you feeling today?

Mr. Colin: CancerBro, I was shocked when I was diagnosed with cancer, but after talking to you, I am feeling better.

CancerBro: What were your symptoms for which you consulted the doctor?

Mr. Colin: I had abdominal discomfort and pain for last several days, and also difficulty in passing stools, that was gradually increasing. Recently, I also noticed blood in stools.

CancerBro: What kind of diet do you take? Do you consume fruits and vegetables regularly?

Mr. Colin: CancerBro, my diet is mostly unhealthy, with fried and processed foods. I rarely consume any fruits and vegetables.

CancerBro: Are you addicted to smoking or alcohol?

Mr. Colin: Yes CancerBro, I smoke heavily and consume alcohol very frequently.

CancerBro: Okay Mr. Collin, thank you very much. I think you people must have got an idea of how a patient with colon cancer presents, and what are the risks factors of the disease.

What are the Risk Factors of Colon Cancer?

Prevalence of colon cancer is more in developed countries, more so in the obese population. And migration to the developed countries also increases the risk of the disease.

But for the past few years, the incidence of colon cancer is decreasing in USA and Canada, whereas it is increasing in China and Japan. Moreover, it’s incidence in the population more than 50 years of age is going down, whereas, it is increasing in young population less than 50 years of age.

A diet that is rich in red meat and fats, and poor in fruits and vegetables, may also increase the risk of colon cancer. Packaged or processed meat may also increase the risk of the disease.

Smoking is also a colon cancer risk factors for the disease, and the risk increases with the duration and intensity of smoking.

Regular and heavy alcohol consumption also increases the risk of colon cancer.

Fresh fruits and vegetables should be consumed regularly to decrease the risk of the disease. Regular physical activity may also help in reducing the risk of the disease. Intake of NSAIDs and calcium has also been found to reduce the risk of colon cancer.

A history of colon cancer in close relatives, especially at a young age, also increase the risk in other family members. So these were the colon cancer risk factors.

colon cancer risk factors

What are the Symptoms of Colon Cancer?

Colon cancer may present as bleeding per rectum, in form of red or black stools.

It may also present as abdominal distention or constipation.

Abdominal pain or weight loss may also be present in majority of patients.

Rarely, jaundice, cough and breathlessness may be present due to the spread of cancer to liver and lungs.

These were the symptoms with which a patient of colon cancer presents commonly.

What are the Investigations for Diagnosis and Staging of Colon Cancer?

Investigations required to confirm and stage the disease are colonoscopy, tumor markers and imaging.

Colonoscopy is one of the most important investigations which is required to confirm the disease. In this, a colonoscope is passed through the rectum into the intestine, that helps in localising the site of the tumor. We can take a biopsy from the tumor for histopathological diagnosis.

Also we can do an endoscopic ultrasound, to assess the depth of infiltration of tumor and involvement of adjacent structures and regional lymp nodes by the tumor.

CT scan of abdomen helps us to assess the local and distant spread of the tumor to other structures. Rarely, PET CT scan may also be required. Imaging of chest with X-ray or CT scan may also be required in some cases, depending upon the symptoms.

Next step is to do blood tests, to check for tumor marker. CEA is the tumor marker for colon cancer. Baseline level of CEA should be done to assess the response to treatment. So these were the investigations required to confirm the diagnosis of colon cancer, and stage the disease.

What is the Normal Anatomy of Colon?

This pouch-like structure, present at the beginning of the colon is called as caecum. caecum This part, present on the right side of the abdomen, extending upwards from the caecum is called an ascending colon. ascending colon The longest part of the colon, that extends from the right to the left side of the abdomen, is called as transverse colon. transverse colon And this part, which extends downwards from transverse colon, on the left side of the abdomen, is called as descending colon. descending colon And this last part, which connects colon to the rectum and anal canal is called as sigmoid colon. sigmoid colon These are the loops of the small intestine that occupy the central part of the abdomen. This is the cross-section from the wall of the colon, with the upper part being inside and lower part being outside of the wall. cross-section from the wall of the colon The innermost layer is epithelium, followed by this layer called as lamina propria.

Outer to which lies muscularis mucosa.

Then comes the submucosa.

Outer to which lies the muscularis propria which is followed by a layer of pericolorectal tissue.

On the outermost aspect, lies this layer which is called as serosa.

What is the TNM Staging for Colon Cancer?


T Staging infographic

Tis – Pre-cancerous or cancer cells present only in the superficial layer (epithelium) of colorectal mucosa

T1 – Cancer extends to the lamina propria

T2 – Cancer extends to the muscular layer (muscularis propria)

T3 – Cancer extends through the muscularis propria into the pericolorectal tissues

T4a – Cancer has invaded up to the outermost serosa layer (or visceral peritoneum)

T4b – Cancer has invaded into the adjacent structures/organs like small intestine, kidneys, pancreas, or stomach.

A tumor present in almost any part of the colon may infiltrate into the small intestine. Tumor in the ascending colon may infiltrate into the right kidney.

And that in the descending colon may infiltrate into the left kidney.

A transverse colon tumor may extend to involve pancreas. And may even extend to involve the stomach.

T staging diagram


Now we will discuss the N staging or the nodal staging for colon cancer. In this figure, you can see the draining lymph nodes for the colon. N staging diagramIt can be called as N0, N1 or N2, depending upon the number of lymph nodes involved.

N0 – Cancer has not spread to regional lymph nodes

N1 – Cancer has spread to 1 to 3 nearby lymph nodes

N2a – Cancer has spread to 4 to 6 nearby lymph nodes.

N2b – Cancer has spread to >/=7 nearby lymph nodes.


Lastly, we will discuss the M-staging or the metastatic staging of the colon cancer.

As you can see in the figure, the venous drainage from most of the part of colon, ultimately pass through the liver. Diagram to show venous drainage passing from most of the part of colon So liver is the most common site for the distant spread of the tumor from colon. As you can see in this figure, the tumor in the right side of colon has spread to the liver. metastasis to liver In this figure, a left sided tumor has spread to the liver. left sided tumor spread to the liver Due to the direction of vascular drainage, after liver, lungs are the second most common organs involved by metastasis. This figure shows the spread of colon cancer to both the lungs, in form of multiple nodular deposits.

And sometimes, both lungs and liver maybe involved in the metastatic spread of the disease, as we can see in this figure. metastasis to both lungs The tumor may also spread to the peritoneum, in form of peritoneal deposits. spread to the peritoneum It may rarely spread to one or both the ovaries. Very rarely, the tumor may also spread to the brain or bones.

M1a – Cancer has spread to one distant organ without peritoneal spread.

M1b – Cancer that has spread to >/=2 distant organs without peritoneal spread.

M1c – Cancer that has spread to peritoneum with or without other sites.

N and M staging infographic

What is the Dukes Staging of Colon Cancer?

  • Dukes A: invasion into but not through the bowel wall
  • Dukes B: invasion through the bowel wall but not involving lymph nodes
  • Dukes C:  involvement of lymph nodes
  • Dukes D: widespread metastases

Weaknesses of Duke Staging

  • Lack of determination of adequacy of nodal sampling
  • Lack of consideration of the extent of LN involvement
  • Lack of consideration of tumour grade

What is the R Staging for margins of Resection?

  • R0-tumours that are completely resected with histologically negative margins
  • R1-tumours with a complete gross resection, but with microscopically +ve margin
  • R2-Incomplete resection with grossly +ve margins

All 3 margins (proximal, distal and circumferential radial margin or CRM) should be commented in pathology report.

What is the Treatment of Colon Cancer?

colon cancer treatment options  

Treatment of Localised and Locally Advanced Colon Cancer

Broadly, colon cancer may be divided into localized or locally advanced disease, and metastatic disease.
First, we will discuss the localized or locally advanced colon cancer treatment.
In T1, the disease extends up to the submucosa.
And in T2, it extends upto the muscular propria.
Now, we will discuss the treatment of T1 or T2 disease, without any lymph node involvement. Surgical resection of the colon is the treatment in these cases, which may be in the form of right or left hemicolectomy.
Surgical resection of the colon Now we come to the treatment of the T3 disease, that is, the disease involving the pericolorectal tissue, without the involvement or regional lymph nodes.
Surgery of the colon is the mainstay of the treatment in these cases, as we have discussed previously, and chemotherapy may be added in selected patients, with high-risk disease.
CancerBro, how is it decided which patients will receive chemotherapy for T3 disease?
It is decided by the oncologist, depending upon the clinical presentation of the patient, tumor marker levels, imaging findings, his pathological report, and performance status of the patient.
Next comes the T4a disease, which extends up to the serosa. Surgery, followed by chemotherapy is the standard treatment for T4a disease.
Now we come to the treatment for T4b disease, that is, the disease which extends through the wall of the colon to involve the adjacent structures.
In this figure, the tumor extends to involve the small intestine.
extends to involve the small intestine Cancer in ascending colon may extend locally to involve right kidney. extends to right kidney And that in descending colon may extend to involve left kidney.
Transverse colon cancer may extend locally to involve pancreas or the stomach. infiltrates into pancreas Surgery and chemotherapy is the standard treatment for most of the patients of T4b disease.
If cancer involves regional lymph nodes, then irrespective of the T status of the patient, chemotherapy should be added to surgery.
spread to regional lymph nodesBut again, the final decision is taken by the oncologist on an individual patient basis, after assessing the performance status and the disease of the patient.
treatment for non-metastatic disease With this, we come to the end of localized or locally advanced colon cancer treatment.

Treatment of Metastatic Colon Cancer

Now, we come to metastatic colon cancer treatment. It may present as metastasis to liver or lungs.

metastasis to liver metastasis to lungs It may also present as metastasis to both, lungs and liver.

spread to both liver and lungs peritoneum in the form of peritoneal or omental deposits.

peritoneal deposits Very rarely, it may also spread to brain or bones. For most cases of metastatic disease, chemotherapy with/without targeted therapy is the treatment of choice.

Metastatic unresectable disease treatment

But CancerBro, surgery was done in my case for metastatic disease?

In some cases of metastasis to liver, when the disease involves only a certain part of liver, surgery maybe possible. liver metastasis So, if initially the metastasis involves a large part of liver. But after giving chemotherapy it regresses to a small part, surgery maybe tried. The final decision to do surgery or not is taken by the oncologist on an individual patient basis, after assessing the exact pattern of liver involvement by the tumor, performance status of the patient along with other factors.

Other modalities are also being used to address the liver metastasis. One such modality is embolization, in which different kinds of substances are injected into the hepatic artery. It is called as chemoembolization if chemotherapy is injected. Radioembolization, if radioisotopes are injected. And arterial embolization, if small particles and beads are injected to block the artery.

hepatic artery embolization Another such method to address the liver metastasis is called an ablation, in which a probe is inserted to destroy the metastatic site.

ablation of liver metastasis It is called as radiofrequency ablation if radio frequency waves are used to destroy the tumor. Microwave ablation, if microwaves are used. Cryoablation, if cold gases are used to freeze the tumor. Percutaneous ethanol injection may also be used to destroy the tumor cells.

Similar to the liver metastasis, if lung metastasis involves a very small part of the lung, which can be removed safely, surgery may be possible. Even in limited metastasis in both liver and lungs, surgery may be tried.

But these are very selective situations, in which a number of factors have to be considered, before taking up for surgery. The final decision is taken by the oncologist on an individual patient basis, after assessing the performance status and disease of the patient in detail.

Metastatic resectable disease treatment

Other modalities like radiotherapy, surgery or bone-directed therapy, may also be used, for palliation or relief of symptom. Always remember that the treatment for metastatic colon cancer is not generally curative, so the main intent for the treatment is a prolongation of life, reduction of symptoms and improvement of the quality of life. With this, we come to the end of metastatic colon cancer treatment.


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