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Colon cancer is one of the types of cancer that can be treated successfully with early diagnosis and correct treatment planning. Thanks in particular to screening programmes and colonoscopy, the disease can be detected before it causes symptoms or while it is still at the stage of a polyp with the potential to turn into cancer.

Overview

Colon cancer is a tumour that develops from the cells lining the inner surface of the large bowel.

A significant proportion of colon cancers initially develop from growths called polyps. Not all polyps turn into cancer; however, some types of polyp carry a risk of cancer developing over the years. This process usually takes a long time. For this reason, colon cancer is one of the cancers that can be detected early through screening and prevented before it develops.

Detecting and removing polyps that may be precursors of cancer during a colonoscopy can reduce the risk of developing colon cancer. In addition, detecting the disease at an early stage increases the treatment options and the likelihood of successful treatment.

For this reason, even if there are no complaints, colon cancer screening is important at the appropriate age and in the appropriate risk group.

Symptoms and Causes

What are the symptoms of colon cancer?

Colon cancer may cause no symptoms at all, especially in the early stages. This is why screening is important.

As the disease progresses, or depending on where the tumour is located in the bowel, the following symptoms may appear:

A new and persistent change in bowel habit
Long-lasting constipation or diarrhoea
Red or dark-coloured blood in the stool
Unexplained iron deficiency or anaemia
Weakness and tiring easily
Abdominal pain, cramps or bloating
A feeling that the bowel has not emptied completely
Unexplained weight loss

Having these symptoms does not necessarily mean colon cancer. Similar complaints can also occur with haemorrhoids, diverticular disease and other bowel conditions.

However, symptoms that are new, recurrent or persistent in particular need to be assessed.

What factors increase the risk of colon cancer?

Colon cancer does not have a single cause. Age, genetic characteristics, lifestyle and certain diseases may all play a part.

The main factors that may increase the risk are:

Advanced age
A history of colon or rectal cancer in first-degree relatives
Having had a colon polyp previously
Inherited syndromes such as Lynch syndrome or familial adenomatous polyposis (FAP)
Long-standing inflammatory bowel diseases such as ulcerative colitis or Crohn’s colitis
High consumption of processed meat
Smoking
Excessive alcohol consumption
Low physical activity
Excess weight and obesity

Having one of the risk factors does not mean that the person will necessarily develop colon cancer. Similarly, colon cancer can also develop in people who have no obvious risk factors.

Is It Possible to Prevent Colon Cancer?

It is not possible to prevent all colon cancers. However, lifestyle changes such as regular physical activity, maintaining a healthy body weight, not smoking and eating a healthy diet can help reduce the risk.

In addition, one of the most important preventive approaches is regular screening of people at risk.

The aim of screening for colon cancer is not only to detect cancer at an early stage. Being able to remove certain polyps with the potential to turn into cancer during a colonoscopy can also help prevent colon cancer before it develops.

How Is It Diagnosed?

When colon cancer is suspected, one of the most important diagnostic methods is colonoscopy.

During a colonoscopy, the inner surface of the large bowel is examined in detail with the help of a camera. If a suspicious area is seen, a biopsy, that is, a small tissue sample, can be taken from it.

The definitive diagnosis is made when the tissue taken is examined under a microscope by a pathologist.

After the diagnosis of colon cancer has been confirmed, imaging methods such as computed tomography (CT) and certain blood tests are usually used to assess whether the disease has spread outside the bowel or to other organs.

This assessment is called staging.

Staging is one of the most important steps in determining the treatment to be given.

When should colon cancer screening start?

For people at average risk, many current international guidelines recommend that colon and rectal cancer screening should start at the age of 45 (American Cancer Society (ACS) colorectal cancer screening guideline, updated in 2026)

However:

In people with colon or rectal cancer in the family,
In people previously found to have polyps with advanced features,
In certain inherited cancer syndromes,
In people with long-standing inflammatory bowel disease

screening may start at an earlier age and be carried out more often.

For this reason, the screening programme should be determined according to the person’s age, family history and personal risk factors.

Screening is not carried out only with colonoscopy. Depending on the person’s risk characteristics, stool-based tests and certain other screening methods may also be used. If a screening test other than colonoscopy is positive, the assessment should be completed with a colonoscopy.

Treatment Options

In colon cancer, the treatment plan is determined according to the location, stage and biological characteristics of the tumour and the patient’s general health.

One of the main methods of treatment is surgery.

How is colon cancer surgery performed?

The main aim of surgery is to remove the section of bowel containing the tumour together with appropriate surgical margins and the regional lymph nodes.

This operation is generally called a colectomy.

The length of bowel to be removed varies according to where the tumour is located. In most patients, after the diseased section of bowel has been removed, the healthy ends of the bowel are joined again. This procedure is called an anastomosis.

Is the operation open or keyhole?

Colon cancer operations can be performed with open surgery or, in suitable patients, with keyhole methods (minimally invasive - laparoscopic surgery).

In laparoscopic surgery, the operation is performed with the help of a camera and surgical instruments inserted through small incisions.

In suitable patients, the laparoscopic approach can offer advantages such as:

Smaller surgical incisions,
Less pain after the operation,
Being able to move about earlier,
A quicker return to daily life

These advantages may be gained in suitable patients.

However, in choosing the surgical method, the priority is always to perform a safe and adequate operation in line with the basic principles of cancer surgery. In other words, the priority is treating the cancer; the benefits linked to the type of operation come second.

The most suitable surgical approach is determined by assessing the location of the tumour, the extent of the disease, previous operations and the patient’s general condition.

Is Chemotherapy Needed in Colon Cancer?

Not every patient with colon cancer needs to receive chemotherapy.

The need for chemotherapy is determined mainly by the stage of the disease and the results of the pathological examination carried out after surgery.

While surgery alone may be sufficient in some early-stage colon cancers, chemotherapy after surgery may be recommended in some patients, particularly those with spread to the lymph nodes or with high-risk features.

In advanced disease, systemic treatments such as chemotherapy, targeted therapies or, in suitable patients, immunotherapy may be considered.

For this reason, it is important that treatment is planned with a multidisciplinary approach.

Is a stoma (bag) needed after colon cancer surgery?

A permanent stoma is not needed in the majority of colon cancer operations.

However, depending on the location of the tumour, the condition of the bowel during the operation, the need for emergency surgery and the patient’s general condition, some patients may need a temporary or, more rarely, permanent stoma.

If a stoma is needed, the reason for it and whether it will be temporary are discussed in detail with the patient before the operation wherever possible.

Recovery

What can I expect after the operation?

The recovery time varies according to the extent of the operation performed, the surgical method used and the patient’s general health.

Today, as part of enhanced recovery protocols after surgery, the aim is for patients to move about as early as possible and, in suitable patients, to start eating and drinking by mouth early.

In the period after the operation:

Pain is controlled,
Early mobilisation is encouraged,
Diet is adjusted gradually,
Bowel function is monitored,
The operation site and the patient’s general condition are assessed.

After discharge, daily activities are resumed gradually. It is important to follow your surgeon’s advice about strenuous physical activity and heavy lifting.

How is follow-up carried out after the operation?

After the operation, the removed tumour and lymph nodes are examined in detail by pathology.

These results make it possible to determine the definitive stage of the disease and to decide whether additional treatment is needed.

After treatment has been completed, follow-up is carried out at set intervals with:

Check-ups with the doctor,
Blood tests,
Imaging methods if necessary,
Colonoscopy.

Follow-up is carried out in this way.

The frequency and duration of follow-up are determined according to the stage of the disease and individual characteristics.

Frequently Asked Questions

Can colon cancer be completely cured?

Yes. Successful and lasting treatment with surgery may be possible, especially in colon cancers detected at an early stage.

The success of treatment depends on many factors, such as the stage of the disease, the biological characteristics of the tumour and the person’s general health.

Does every colon polyp turn into cancer?

No.

Not all colon polyps turn into cancer. However, some types of polyp carry a risk of cancer developing over time.

For this reason, it is important that polyps detected during a colonoscopy are removed appropriately and examined by pathology.

Is a colonoscopy painful?

As a colonoscopy is usually carried out under sedation, most patients do not feel significant discomfort during the procedure.

For the procedure to be safe and successful, it is important that the bowel preparation before the colonoscopy is carried out correctly.

Will I definitely need a bag after colon cancer surgery?

No.

A permanent stoma is not needed in most colon cancer operations. The need for a stoma varies according to the location of the tumour, the type of operation and the patient’s clinical condition.

There is colon cancer in my family. When should I start screening?

This depends on how closely related your relative diagnosed with cancer is and the age at which they were diagnosed.

In particular, people who have first-degree relatives with colon or rectal cancer may need to be assessed earlier than the standard screening programme.

For this reason, it is important that the family history is assessed in detail and that an individual screening programme is drawn up.

Does Colon Cancer Have the Same Characteristics in Every Patient?

No. Today it is not enough to assess colon cancer only according to its location in the bowel and its stage. The pathological, molecular and genetic characteristics of the tumour are also becoming increasingly important in treatment planning.

One of the most important of these is the Mismatch Repair (MMR) / Microsatellite Instability (MSI) status.

The MMR system is involved in correcting certain errors that can arise in DNA during cell division. Tumours with a defect in this system may be described as dMMR, and tumours showing high microsatellite instability as MSI-H.

Knowing the MMR/MSI status can contribute to:

Assessing inherited cancer predispositions such as Lynch syndrome,
Better understanding the biological characteristics of the disease,
Making the decision on chemotherapy after surgery in some patients,
Assessing treatments such as immunotherapy in advanced disease.

It can be helpful in all of these areas.

For this reason, in the modern approach to colon cancer, not only the question “What stage is the tumour?” but also the question “What are the biological characteristics of the tumour?” has become important.

How Does Treatment Change According to Stage?

One of the main determinants of colon cancer treatment is the stage of the disease. However, the treatment decision is not made according to stage alone; pathological risk factors, the biological characteristics of the tumour, the patient’s age and general health are assessed together.

Stage I: The disease is confined to the bowel wall. Appropriate oncological surgery provides sufficient treatment in most patients, and chemotherapy after surgery is generally not needed.

Stage II: The tumour has reached a deeper level in the bowel wall, but no cancer has been found in the regional lymph nodes. Not all of these patients routinely receive chemotherapy. Certain high-risk features, such as a T4 tumour, bowel obstruction or perforation, lymphovascular/perineural invasion and an insufficient number of lymph nodes examined, can affect the treatment decision. MMR/MSI status is also particularly important at this stage.

Stage III: The cancer has spread to the regional lymph nodes. After surgery, adjuvant chemotherapy is given to a significant proportion of patients to reduce the risk of the disease recurring.

Stage IV: The cancer has spread to the liver, lungs, peritoneum or other organs. However, the presence of metastases does not always mean that surgical treatment is not possible. Especially in selected patients with limited liver or lung metastases, different combinations of surgery, local treatments and systemic treatments may be considered.

For this reason, especially in advanced colon cancer, it is important that treatment is planned individually by a multidisciplinary team.

Why Is the Pathology Report After Surgery Important?

The section of bowel and the lymph nodes removed in colon cancer surgery are examined in detail by a pathologist.

The pathology report does not only give the cancer diagnosis; it also assesses features such as:

The depth to which the tumour has grown into the bowel wall,
Whether there is tumour in the lymph nodes,
The number of lymph nodes examined,
The surgical margins,
Lymphatic or vascular invasion,
Perineural invasion,
The degree of differentiation of the tumour and other histopathological features

which can affect the stage of the disease and subsequent treatment decisions.

Particularly in stage II colon cancer, some of these features are important in assessing the risk of the disease recurring and in the decision on chemotherapy after surgery.

For this reason, although surgery is an important step in colon cancer treatment, the final treatment plan is often shaped after the pathology report following surgery has been completed.

Can Molecular Characteristics Change Treatment?

Yes. Especially in advanced colon cancer, determining the molecular characteristics of the tumour can help in assessing personalised treatment options.

In addition to MMR/MSI status, the assessment of molecular markers such as RAS and BRAF may be considered, depending on the stage and clinical features of the disease.

These results can be used to determine in which patients certain targeted therapies or immunotherapy may be beneficial.

Thanks to these developments, colon cancer treatment today is increasingly moving from a “same treatment for every patient” approach towards a “personalised treatment” approach.

Does Treatment End with Surgery?

In colon cancer treatment, regular follow-up is important after surgery and any oncological treatments given. In addition, increasingly strong scientific evidence is emerging on the importance of healthy lifestyle habits in the period after treatment.

The CHALLENGE phase III randomised trial, published in the New England Journal of Medicine in 2025, compared a structured exercise programme with health education in colon cancer patients who had completed surgery and adjuvant chemotherapy. This study is one of the pieces of high-level evidence showing that physical activity after colon cancer treatment may be important not only for general health and quality of life but also for oncological outcomes.

However, the exercise programme needs to be planned appropriately, taking into account the person’s age, general health, surgery and oncological treatments.

Scientific References

The information on this page has been prepared on the basis of current international guidelines and high-level scientific studies.

American Cancer Society (ACS). Colorectal Cancer Screening Guideline. 2026 update.
American Society of Clinical Oncology (ASCO). Adjuvant Therapy for Stage II Colon Cancer: ASCO Guideline Update. Journal of Clinical Oncology.
National Comprehensive Cancer Network (NCCN). Clinical Practice Guidelines in Oncology: Colon Cancer.
European Society for Medical Oncology (ESMO). Clinical Practice Guidelines for Colon Cancer.
American Society of Colon and Rectal Surgeons (ASCRS). Clinical Practice Guidelines for the Management of Colon Cancer.
Courneya KS, Vardy JL, O’Callaghan CJ, et al. Structured Exercise after Adjuvant Chemotherapy for Colon Cancer. N Engl J Med. 2025;393:13–25. doi:10.1056/NEJMoa2502760.

Important Information: The information on this page has been prepared for general information purposes, drawing on current scientific literature and international guidelines. The clinical characteristics of every patient are different; the information given here does not replace a personal medical assessment, diagnosis or treatment recommendation. People with suspected colon cancer, symptoms or risk factors should see a doctor for a personal assessment.