What exactly is colorectal cancer?

The second most common cancer

All malignant tumours located in the colon and rectum are referred to as colorectal cancer or bowel cancer. According to estimates by the Robert Koch Institute, 33,400 men and 27,600 women were diagnosed with colorectal cancer and approximately 25,000 people died from its consequences in 2016 in Germany alone.1

The main reason for this lies in late detection: Currently, 71% of diagnoses are made in later stages (C & D) of the disease.1

Darmkrebs Illustration

1) Centre for Cancer Registry Data, Robert-Koch-Institute (2017). Krebs in Deutschland, 11th Edition.

How does colorectal cancer develop?

Colorectal cancer often develops from polyps.

In most cases, colorectal cancer develops from polyps. These are initially benign cell clusters that occur in many people. However, the cells of the polyps can undergo genetic changes, causing the cells to mutate and become precursors of colorectal cancer called adenomas.2

The classification of colorectal cancer stages is often based on the so-called Dukes Stages:


Dukes Stage A

The tumour is restricted to the superficial cell layers of the intestine.


Usually simple surgery3

Five-year survival rate:
95 %4

Dukes Stage B

The tumour is enlarged and can extend fully throughout the intestinal wall.


Surgery & Chemotherapy3

Five-year survival rate:
85 %4

Dukes Stage C

Colorectal cancer spreads to the nearby lymph nodes.


Surgery & Chemotherapy3

Five-year survival rate:
50 %4

Dukes Stage D

Colorectal cancer has metastasized and spread to other organs.


Surgery & Chemotherapy3

Five-year survival rate:
8 %4

 2) Cotton PB et al. (2004). JAMA 291(14), 1713–1719. 3) German Cancer Society, German Cancer Aid, AWMF (2019). Leitlinienprogramm Onkologie, Langversion 2.0. AWMF Registrierungsnummer: 021/0070L. [https://www.leitlinienprogramm-onkologie.de/leitlinien/kolorektales-karzinom/, Retrieved: 23.01.2020] 4) Schatz D (2010). Diss., University of Potsdam. LNA-clamp-PCR zum sensitiven Nachweis von Punktmutationen im Rahmen der Entwicklung eines Darmkrebsfrüherkennungstests.

Which symptoms usually occur?

During early stages, colorectal cancer has "silent symptoms"

One of the main reasons for the large number of late diagnoses is the mostly symptom-free development of colorectal cancer. Symptoms are rare in early stages, which is why patients often do not see a doctor until the disease has already progressed.

In order to protect oneself sufficiently against severe colorectal cancer, it is essential to take precautions even before symptoms occur.

Common symptoms of colorectal cancer include4:


  • persistent diarrhea
  • cramping stomach ache
  • blood in the stool
  • chronic constipation

4) German Cancer Research Center (2019).[https://www.krebsinformationsdienst.de/tumorarten/darmkrebs/symptome.php, Retrieved: 10.12.2019].

Who should be screened?

Starting at the age of 50, the risk of colorectal cancer rises rapidly

One of the major risk factors for colorectal cancer is age. The continuous natural division of the intestinal cells becomes increasingly unreliable - there are more and more defects in DNA duplication. This can lead to mutations that promote the development of colorectal cancer.5

The oncological S3 guideline recommends colorectal cancer screening from the age of 50.7 If other risk factors apply, it is advisable to take precautions at an earlier time.

Other risk factors include:6


Family history of

colorectal cancer

Obesity and lack of


Consumption of

alcohol and tobacco

Consumption of

red meats

5) Figura G et al. Onkologie 32 (Suppl 3) (2009), 34-38. 6) Johnson CM et al. (2013). Cancer Causes & Control 24(6), 1207-22. 7) German Cancer Society, German Cancer Aid AWMF (2019). Leitlinienprogramm Onkologie, Langversion 2.0. AWMF Registrierungsnummer: 021/0070L. [https://www.leitlinienprogramm-onkologie.de/leitlinien/kolorektales-karzinom/, Retrieved: 23.01.2020]

Which screening options are available?

In the field of colorectal cancer screening, the colonoscopy is currently considered to be the so-called gold standard. This refers to medical solutions by which other methods are measured in terms of their analytical quality.


The german medical guidelines for colorectal cancer screening recommend two colonoscopies at a ten-year interval starting at the age of 50 for men and 55 for women. From the age of 50 onward, an occult blood test is available as an annual or biannual alternative.



After bowel cleansing, an endoscope is used to examine the colon for cancer (precursors) and polyps. Patients can be given a sedative upon request.


Most precise screening method, immediate removal of polyps possible


Extensive intestinal cleansing, invasive surgery, loss of working hours


Occult blood test (FIT)


Simple stool test in which the patient's sample is examined by a laboratory for hidden blood. This can be an indirect sign of colorectal cancer.



Simple procedure at home without medical intervention


Misses tumours that do not bleed and therefore up to 37% of colorectal cancer cases per procedure8

8) Gies et al. (2018). Gastroenterology 154(1), 93-104.

ColoAlert combines the advantages of both methods

Through the analysis of tumour DNA, ColoAlert detects significantly more cases of colorectal cancer than other stool tests and allows for an earlier diagnosis in those affected - all in a simple at-home stool test!