Colorectal cancer
Colorectal cancer most often develops from benign polyps in the colon or rectum over several years. Early detection is decisive for the prognosis, and colonoscopy is the most important examination.
The Surgeon's Guide to Bowel Cancer: Diagnosis, Staging and Advanced Treatment
Bowel cancer (also known as colorectal cancer) is the collective term for cancer in the colon and rectum. The diagnosis is serious, but outcomes have improved markedly in recent years. Modern surgical techniques combined with precision medicine and new treatment strategies now give far better prognoses and quality of life than before.
With around 4,000 new cases each year in Denmark, prevention and early diagnosis are essential, and colonoscopy plays the most important role here.
Why does bowel cancer occur? From polyp to cancer
Almost every case of bowel cancer starts as benign clusters of cells (growths) in the bowel lining, called polyps.
Normally cells only divide when needed, but if the control mechanisms fail, the mucosal cells grow uncontrollably. Over time, some of these polyps (specifically adenomas) can become autonomous and develop into cancer. The process typically takes several years.
Early detection and removal of polyps through regular colonoscopy is the most effective prevention of bowel cancer.
Symptoms: When should you see a doctor?
The symptoms of colon and rectal cancer vary, but you should always see a doctor as soon as possible if you notice any of the following:
Bleeding and anaemia
- Blood in the stool or on the toilet paper: Bleeding is often mistaken for haemorrhoids but can be a sign of cancer. Read more about rectal bleeding.
- Unexplained anaemia: Prolonged, hidden bleeding from the bowel can lead to anaemia, which shows up as fatigue and pale skin. Minor bleeding can be detected by a stool test for blood.
Changes in bowel function
- Changes in stool: Altered frequency, consistency or noticeably thinner calibre of the stool over weeks.
- A feeling of incomplete emptying after passing stool (typical of rectal cancer).
Bowel obstruction
If the tumour grows large enough, it can fully or partially block the bowel (obstruction), which can cause:
- A distended, bloated abdomen.
- Unexplained weight loss, nausea and vomiting.
- Abdominal pain (rarely in early colon cancer).
- Rectal pain (seen mainly when rectal cancer grows into surrounding tissue).
Diagnosis: How is bowel cancer diagnosed?
To diagnose bowel cancer and plan the right treatment, you go through a series of specialised examinations:
- Initial examination: The doctor inserts a finger into the rectum (digital rectal exam) to feel for lumps in the lower part.
- Endoscopy (colonoscopy): The gold standard for examining the bowel. A flexible tube is passed through the anus. Colonoscopy makes it possible to visualise the entire colon and rectum, take tissue samples (biopsies) and remove polyps. See the other endoscopic examinations offered at the clinic.
- Microscopy of tissue samples: If cancer is suspected during colonoscopy, tissue samples will be taken for microscopic examination. The samples are examined for cell changes and various markers, including MMR status (Mismatch Repair). This maps the tumour's biology early on and is important for choosing the right medical treatment or immunotherapy.
- CT colonography ("virtual colonoscopy"): If a colonoscopy cannot be completed (for example if the bowel is too narrow), a CT scan of the colon and rectum is used as a quick and equally valid diagnostic alternative.
- Staging (scans): If cancer is found, it is investigated for possible spread using:
- CT scan of the chest and abdomen.
- MRI and/or ultrasound through the rectum (specifically for rectal cancer, to assess local extent).
Disease stages: TNM classification
To assess the best treatment and prognosis, bowel cancer is divided into stages using the international TNM system, which describes how far the disease has progressed:
- T (Tumour): Local growth of the tumour (T1-T2 are limited to the bowel wall; T3-T4 have grown deeper or through the bowel wall).
- N (Node): Whether the cancer has spread to nearby lymph nodes (N0 means no spread; N1-N2 means spread to lymph nodes).
- M (Metastasis): Whether there is spread to other organs, for example the liver or lungs (M0 means no distant spread; M1 means spread).
The four cancer stages
| Stage | TNM criteria | Description and prognosis |
|---|---|---|
| Stage 1 | T1-2, N0, M0 | Small tumour, no spread to lymph nodes or other organs. Best prognosis. |
| Stage 2 | T3-4, N0, M0 | Larger tumour, but still no spread to lymph nodes or other organs. |
| Stage 3 | T1-4, N1-2, M0 | The cancer has spread to local lymph nodes, but there is no distant spread. |
| Stage 4 | Any T, any N, M1 | Spread to other organs in the body (metastases). |
All stages can today be treated with the aim of cure, but the risk of recurrence depends on the stage and the tumour biology.
Treating bowel cancer: A tailored, multidisciplinary approach
Treatment is highly specialised and adapted to the individual patient in close cooperation between surgeons and oncologists.
Surgical treatment (operation)
Surgery remains the cornerstone of treatment. Most centres now offer keyhole surgery (laparoscopic or robot-assisted), where the surgeon operates through small incisions. This means less pain and faster recovery.
- Surgery for colon cancer: The cancer, a section of healthy bowel on either side and the surrounding fatty tissue with lymph nodes are removed. The bowel is usually joined back together immediately.
- Surgery for rectal cancer: All or large parts of the rectum are removed together with the surrounding fatty tissue (mesorectum) to reduce the risk of local recurrence.
- Temporary stoma: Often created to protect the bowel join and let the bowel rest while it heals.
- Permanent stoma: Necessary if the tumour sits so close to, or involves, the sphincter that the sphincter must be removed.
Medical and oncological treatment (before and after surgery)
Treatment is given either to support surgery, to shrink the tumour beforehand or as palliative care.
- Treatment BEFORE surgery (neoadjuvant treatment):
- For rectal cancer, radiotherapy is used, often combined with chemotherapy, to shrink the tumour before surgery.
- Following the latest guidelines, medical treatment (chemotherapy or targeted immunotherapy) is now also increasingly offered before surgery for colon cancer if the tumour is locally advanced or has specific genetic features (for example dMMR/MSI-high).
- Treatment AFTER surgery (adjuvant treatment): Chemotherapy is offered after surgery (especially for stage 3 and selected stage 2) to remove any microscopic cancer cells and reduce the risk of recurrence.
A modern option: "Watch and Wait" (organ-preserving strategy)
For a selected group of rectal cancer patients who receive intensive radio- and chemotherapy before the planned surgery, the tumour can sometimes disappear completely (complete clinical response). Following the latest guidelines, in these special cases, and under very close follow-up with scans, surgery can be postponed to preserve natural bowel function and avoid a stoma.
Prevention: Can I lower my risk?
Yes, there is a lot you can do yourself.
The best prevention is to take part in the national screening programme for colon and rectal cancer (ages 50-74) and to have a colonoscopy if there are signs of hidden blood in the stool or if symptoms appear.
Beyond that, lifestyle plays a significant role:
| Factors that INCREASE risk | Factors that DECREASE risk |
|---|---|
| Overweight and a high calorie intake | Regular physical activity (exercise) |
| High intake of red and processed meat | Plenty of fruit, vegetables and berries |
| High alcohol consumption | A fibre-rich diet (whole grains) |
| Smoking | Intake of fish and low-fat dairy |
The prognosis
Survival for patients with bowel cancer is improving steadily in Denmark thanks to earlier detection, better screening and more targeted medicine. Average 5-year survival rates are highest in the early stages, but the most important point is that treatment today is fully tailored to the individual patient and the specific biology of the tumour.
CONTACT INFORMATION
Hans Edvard Teglers Vej 9, 1st floor. 2920 Charlottenlund
APPOINTMENT BOOKING
We are on the phone Monday to Thursday
from 09:00 to 12:00
FOR REFERRING PHYSICIANS
Provider number 215430
How to book
Online booking is not available. Call the clinic or ask your GP for a referral.
With a referral from your GP, treatment is free under the Danish public health insurance.
Call the clinic
+45 39 64 01 25
Phone hours
Phone hours: Mon–Thu 09:00–12:00
Address
Hans Edvard Teglers Vej 9, 1st floor · 2920 Charlottenlund
Frequently asked questions
What is bowel cancer?+
Bowel cancer (colorectal cancer) is the collective term for cancer in the colon and rectum. Almost every case develops over several years from benign polyps in the bowel lining. With around 4,000 new cases each year in Denmark, it is one of the most common cancers, but early detection markedly improves the prognosis.
What are the early symptoms of bowel cancer?+
Typical symptoms include blood in the stool, a change in bowel habit (frequency, consistency or thinner calibre) lasting weeks, a feeling of incomplete emptying, unexplained weight loss, fatigue or iron deficiency. Rectal bleeding is often mistaken for haemorrhoids but should always be assessed by a specialist.
How is bowel cancer diagnosed?+
Diagnosis is made by colonoscopy, where a flexible scope is passed through the anus to inspect the entire colon and rectum, remove polyps and take biopsies. If colonoscopy cannot be completed, CT colonography (virtual colonoscopy) can be used as an equally valid alternative. Once cancer is confirmed, CT and MRI scans assess the extent of disease.
What is MMR status and why does it matter?+
MMR (Mismatch Repair) tests the tumour's ability to repair DNA errors. If MMR is deficient (dMMR/MSI-high), the cancer often responds particularly well to immunotherapy. The test is performed routinely on the biopsy and is decisive for choosing medical treatment and for whether treatment can be offered before surgery.
Can bowel cancer be cured?+
Yes. All stages are treated with the aim of cure, and the chance is greatest the earlier the cancer is found. In stage 1, 5-year survival is very high, and even in stage 4 modern surgery, chemotherapy and targeted immunotherapy can give long-term disease control. Treatment is planned individually by surgeons and oncologists together.
What is "Watch and Wait" for rectal cancer?+
In selected patients with rectal cancer, intensive radio- and chemotherapy before the planned operation can make the tumour disappear completely (complete clinical response). Following the latest guidelines, surgery can in these cases be postponed under close follow-up with scans and colonoscopy, so natural bowel function is preserved and a stoma is avoided.
How can I prevent bowel cancer?+
The most important prevention is taking part in the national screening programme (stool test every two years from ages 50 to 74) and having a colonoscopy if tests are positive or symptoms appear. Lifestyle also matters: keep a healthy weight, be physically active, eat a fibre-rich diet with fruit and vegetables, limit red and processed meat and alcohol, and do not smoke.