Bowel cancer

Bowel cancer, also known as colorectal cancer, refers to malignant tumours growing in the large intestine or rectum. While carcinoma of the large intestine or rectum are some of the most common tumours found in humans, carcinoma are rarely found in the small intestine.

Colorectal cancer forms when cells in the lining of the intestines develop into cancer cells. Benign pre-cancerous polyps, called adenomas, initially form from the healthy tissue in the lining of the intestine. However, the cells they contain have a tendency to change over time and to develop into cancer over the course of several years during a process known as the adenoma-carcinoma sequence. The structure of the tissue, and the size and number of adenomas ultimately determine the risk of developing bowel cancer.

The exact causes of colorectal carcinoma are not yet fully understood. However, a lack of exercise, obesity, a bad diet and smoking are all considered to be risk factors. Genetic factors also seem to play a role. There are hereditary forms of bowel cancer, where it is advisable for members of the cancer patient’s family to undergo genetic tests.

Age also plays a role, as the older a person is, the higher the risk of contracting bowel cancer. More than half of all bowel cancer patients are over 70 years of age and approximately 90% of all cancer found in the large intestine occurs in people over 50 years of age.


Bowel cancer does not cause any symptoms in the early stages. In more advanced stages, this type of cancer also often has rather unspecific symptoms that are also associated with other medical conditions. These include:
- Sudden diarrhoea
- Sudden constipation
- Alternating between constipation and diarrhoea (paradoxical diarrhoea)
- Listlessness
- Unintentional passing of stools while passing wind
- Abdominal pain
- Tiredness
- Possible loss of weight
- High temperature
- Nightly sweats
- Shape of stool has changed and is thin like a pencil
- Stools contain blood



The course of treatment for a patient suffering from colorectal carcinoma is defined during interdisciplinary meetings known as tumour boards. These meetings involve not only specialists in oncology, surgery and gastroenterology, but also doctors specialising in nuclear medicine, radiology, pathology and radiology. These specialists form part of the Comprehensive Cancer Centre at Universitätsklinikum Erlangen, which is certified by the German Cancer Society. A patient’s individual treatment depends, among other factors, on the location (large intestine or rectum) and stage of the tumour, as well as on the patient’s age and general health.

If the cancer cannot be treated using surgery, the first step is to examine the tumour tissue using molecular pathology to detect certain genetic changes. In conjunction with the aim of the therapy and the patient’s general health, the results are used to select a suitable treatment.

These treatments include chemotherapy, targeted therapy, radiotherapy and immunotherapy for a sub-group of patients.

Immunotherapy is one of the most up-to-date treatment options available to patients of bowel cancer. Immunotherapy refers to methods that utilise the body’s immune system to fight cancer. These therapies use various approaches, which all strengthen the body’s existing defence mechanisms and direct them to specifically attack cancer cells.

In the case of bowel cancer, the aim of the treatment is to activate the immune system using medication. The drug pembrolizumab has been available to patients with confirmed microsatellite instability (damage to certain DNA repair proteins) as an approved treatment since the end of December 2020. The medication docks onto the PD1 receptor of cancer cells, thus inhibiting interaction with surface protein PD-L1. This protein is expressed by the tumour cells themselves and sends signals to the immune system that there is no danger. The protein thus protects the tumour cells from being attacked by the body’s immune cells. As a PD1 inhibitor, pembrolizumab can reactivate the body’s anti-tumour immune response by counteracting this signal and ensuring that the body detects the cancer cells and destroys them.

At the DZI and its participating hospitals, research is currently being carried out to discover to what extent other groups of patients could also benefit from immune therapy.


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