Colon cancer includes cancers of the colon and the rectum (rectal cancer). Together, they are known as colorectal cancer. Colon cancer can develop in all sections of the colon and the rectum. A core area is in the descending part of the colon, in the lowest 30 to 40 centimetres. Colon polyps are precursors of the cancer in many cases. These are initially benign, fungus-like growths in the colon. Around 90 per cent of colon cancers develop because these polyps mutate, i.e. their cells turn into cancer cells.
In both sexes, colon cancer is the second most common tumour disease. Currently, around 38,000 men and 31,000 women develop colon cancer in Germany every year. Colon cancer mostly occurs in patients older than 50. The average age in men is 69 years, in women it is considerably higher at 75 years. The life-time risk of developing colon cancer is approximately 6 per cent.
There is often a disposition for the disease. Certain dietary and lifestyle habits can have an impact on the development of colorectal cancer. People with benign or inflammatory bowel diseases are also at risk.
A healthy diet with fruit and vegetables has a noticeably positive effect. Food high in vitamins and minerals helps decrease the risk of developing the disease.
Fatty food on the other hand increases the risk of developing colon cancer. Animal fats in particular, and thus the frequent consumption of meat and processed meat products (e.g. cold cuts) can increase the risk. Studies have shown that there are distinctions among the different types of meat: frequent consumption of “red meat” (beef, pork, lamb) increases the risk while the frequent consumption of “white meat” (fowl) and fish decreases the risk. It is well-known that cooking meat and meat products above certain temperatures releases flavouring substances that can be carcinogenic.
Several studies have shown that people with occupations with mainly seated activity have a higher risk of developing colon cancer. In professions with physical activity or in people who are generally physically very active the risk of developing the disease is lower. It was proven that the risk increases the longer a person performs mainly seated activities.
Excessive weight, lack of exercise and nicotine addiction should be avoided.
90 per cent of all colon-cancer patients can be cured if the diagnosis is made early. In colon cancer in particular screening is very important. For this reason, regular screening and check-ups are covered by the national health insurance providers for all people over 50.
Physicians have three diagnostic methods at their disposal:
- fecal occult blood test (FOBT)
- colonoscopy, incl. tissue samples if required
During a palpation exam physicians will gently feel along the rectum. Rectal carcinoma located close to the anus can be detected early and sometimes at a preliminary stage with palpation.
The fecal occult blood test reveals hidden, non-visible blood in the stools. However, not all cancers or all preliminary stages cause the presence of blood in the colon.
A colonoscopy is currently the safest method for colon-cancer screening. During a colonoscopy adenoma, the precursors of colon cancer, can be detected and in some cases even removed during the same session.
If colon cancer is suspected different examinations are initiated. They are used to determine whether a tumour is present. If this is the case, physicians will determine how advanced the tissue changes are.
The most important examinations to determine the presence of a tumour include:
- Palpation (rectal-digital examination)
- Fecal occult blood test (FOBT)
- Proctoscopy (rigid examination of up to 20 cm of the rectum)
- Sigmoidoscopy (flexible part examination)
- Colonoscopy (flexible examination of the entire colon)
- X-ray with contrast agents (contrast enema)
If colon cancer is confirmed further examinations will follow. These serve to determine the spread of the tumour to surrounding tissue and other organs.
The most important examinations to determine the presence of colon cancer include:
- Ultrasound (sonography/endosonography)
- Computer tomography (CT)
- Magnetic resonance imaging (MRI)
- Laboratory tests
The necessary treatment measures can only be determined once all examinations have been concluded.
Once the diagnosis of colon cancer has been made, the physicians involved will talk patients in detail through the treatment strategy best suited to them.
The following therapy options are available:
- Radiation therapy
- Combination of radiation therapy and chemotherapy (radio-chemotherapy)
- Targeted therapy, immunotherapy
- Physical procedures (cryotherapy, heat treatment, high frequency methods and laser treatments)
Regardless of the stage of the disease, the tumour is operated on in most cases. During surgery, complete resection of the tumour and the surrounding lymph nodes is attempted. This is particularly promising in the early stages of colon cancer and increases the chances of a complete cure. Surgery is also attempted in the more advanced stages of colon cancer.
During radiation therapy, cancer cells are destroyed by high-energy radiation. It is used to shrink the tumour before surgery and thus improve the prognosis after surgery. Radiation therapy is usually not used alone but in combination with chemotherapy. This is known as radio-chemotherapy.
If complete resection of the tumour was not possible by surgical means or there is a suspicion that there are cancer cells remaining elsewhere in the body, chemotherapy is usually administered. In many cases, chemotherapy is administered before surgery to shrink the tumour or metastases in advance. Even after complete resection of the tumour, supportive chemotherapy or radio-chemotherapy may be indicated. This can help lower the risk of recurrence significantly. Chemotherapy is also used to check the course of the disease and to improve the patient’s quality of life.
Cytostatics in the treatment of colon cancer
The medicinal products used in chemotherapy are called cytostatics. Today, physicians can choose from a wide range of different cytostatics. They can be combined in order to increase their efficacy. Cytostatics attack all dividing cells. They work particularly well on cells that divide rapidly such as cancer cells. Cytostatics thus inhibit the growth of the tumour. In addition they spread throughout the body with the blood and thus reach the cancer cells in any metastases.
For the treatment plan it is very significant how far advanced the disease is. In order to determine the stage of the disease, in a process known as “staging“, various different examinations are needed, which may take several days or even weeks.
In almost all colon cancer cases, surgery is necessary. This is not only the first important treatment step but also provides significant clues to the actual stage of the disease. It is only possible after surgery to say with any certainty how far the tumour has spread in the colon, how deeply it has invaded the intestinal walls and what kind of metastases were formed in the lymph nodes and the surrounding organs. In addition, the actual aggressiveness of the cancer can only be determined after the characteristics of tumour tissue removed during the surgery have been examined through a microscope (“grading“).
Once all important information is available, physicians will summarise the data on that particular colon cancer in short descriptions of the disease stages.
The stage of the disease is described in terms of the TNM classification. This system uses three markers:
- T is for tumour and describes the size and spread of the tumour; in the case of colon cancer this refers to the tumour in the colon.
- N is for the surrounding lymph nodes (N for nodes; from the Latin for knots) that have been invaded by the tumour cells.
- M is for the lack or presence of (distant) metastasis, i.e. distant metastatic growths in other organs.
The letter is followed by a number which denotes the respective T, N or M stage.
T1-4 and Tis: T is for tumour; the higher the number the further the cancer has invaded the intestinal wall or the surrounding tissue.