Malignant colorectal tumors occupy an inglorious top position in industrialized countries: They rank third among cancers in both men and women. In 2018, 1.8 million people worldwide had colorectal cancer. Almost all malignant neoplasms originate from the glandular tissue of the mucosa of the colon (adenocarcinoma); cancer of the small intestine is very rare.
Where exactly does the cancer originate?
By far the most common type of colorectal cancer occurs as colorectal carcinoma. This means that the cancer is located in the area of the colon (colon carcinoma), which is a part of the large intestine between the rectum and the appendix, and/or in the area of the rectum (rectal carcinoma). Since not only the colon but also the appendix with its vermiform appendix belongs to the large intestine and the rectum up to the anus is in turn an independent section behind the colon, the common terms colon cancer or colorectal cancer are actually inaccurate.
Causes of colorectal cancer
The vast majority of carcinomas arise from benign mucosal growths (adenomas, polyps). The likelihood of degeneration depends on the histologic structure and size (one centimeter or more) of the benign growth. Due to increasing mutations, the cells differ so much from the original structure that they develop an unregulated and uncontrolled growth. They lose contact with other intestinal cells, leave the cell association and penetrate the surrounding tissue. If they get into blood or lymph channels, they can be carried throughout the body and form metastases. Most commonly, degenerate tissue develops in the rectum. The further up the colon you go, the less commonly it is encountered. As the disease progresses, offshoots may develop, especially in the liver and, if the carcinoma is located deep down (in the lower rectum), also in the lungs. From these organs, further spread to the entire organism can occur. People who have a tendency to form intestinal polyps due to genetic predisposition are particularly at risk of developing colorectal cancer. For example, there are certain genetic diseases (familial adenomatous polyposis = FAP) that, if left untreated, will always lead to colorectal cancer. In addition, cigarette smoking – as with almost all types of cancer – also promotes malignant proliferation. Certain operations in the colon area (for example, the connection of the ureters with the colon) or chronic inflammation of the digestive organs (ulcerative colitis) are also associated with an increased risk of cancer.
Dietary influences
In addition, dietary influences are known: Diets high in meat and fat, low in fiber, and obesity are major risk factors. They cause the stool to remain in the intestine for a longer period of time, thus increasing the contact time with the mucosa. This irritates the intestinal mucosa leads to increased toxins entering the intestinal cells – increasing the likelihood that they will multiply uncontrollably.
Symptoms of colorectal cancer
For a long time, colorectal cancer often causes no symptoms or at best mild and uncharacteristic symptoms. For this very reason, people over the age of 45 should be particularly alert to the following signs that require clarification:
- Any change in bowel habits (frequent bowel movements at unusual times, persistent diarrhea or/ and constipation).
- Abdominal cramps and painful bowel movements.
- Flatulence, frequent nausea, or unusual feeling of fullness
- Blood or mucus in the stool (even with known hemorrhoids), very thin stools caused by intestinal constrictions, extremely malodorous stools.
Many of these complaints, such as diarrhea or constipation, can have very different causes and would not have to be a sign of colon cancer. However, if in doubt, a doctor should always be consulted, especially if the complaints persist over a long period of time or are recurrent. Blood in the stool should also be clarified by a doctor, even if the affected person suffers from hemorrhoids – these are so common that cancer and hemorrhoids can occur at the same time. Any cause of blood in the stool must be thoroughly investigated to rule out possible cancer. Cancer: these symptoms can be warning signs
Screening for colorectal cancer
If colorectal cancer is suspected, the family doctor is first the right contact. If necessary, he can refer the affected person to a gastroenterologist.After a discussion of the medical history, the physician can also perform an occult blood test (hemoccult test). For this purpose, a stool sample is examined in the laboratory for very small amounts of blood. If the test is positive, this does not necessarily indicate colorectal cancer. Other diseases, such as hemorrhoids, can also cause blood in the stool. A blood test can also provide initial indications. Depending on the stage of the disease, some patients may have a tumor-derived protein (tumor marker) called carcino-embryonic antigen (CEA) in their blood. While this is not suitable for new detection of colon cancer, as it is not unique to this type of cancer, its determination can be used in follow-up (if the concentration rises again, it is a sign that the cancer is [again] active). In most cases, colorectal cancer is detected by palpation of the rectum and by colonoscopy. To get an idea of the histological type and the degree of degeneration (dysplasia), the physician performs a tissue sampling (biopsy) at the same time. If a colonoscopy does not provide the desired information, there is the option of an X-ray examination with contrast medium. Ultrasound, X-ray examinations, and computed tomography are used to determine the extent of the cancer and the presence of metastases.
Stages and chances of cure in colorectal cancer
Important for prognosis is how far the cancer has penetrated the bowel wall at the time of diagnosis and where it is growing. The closer it is to the anus, the worse the prognosis, because it can spread its daughter tumors more easily from there via lymphatic and blood vessels. If the malignant tumor cells are confined exclusively to the intestine, the chances of cure are very good. Even if the intestinal wall is exceeded and lymph nodes are affected, more than half of the patients can still be cured. If there are several liver metastases, however, the probability of survival is (still) low; if there is only one metastasis, however, there is hope of cure. The earlier a finding (polyp or cancer) is detected, the smaller the intervention and the better the prognosis. The goal of therapy is to cure the affected person of his or her cancer (curative therapy). Age and general condition as well as the extent of the tumor are important influencing factors. In general, colorectal cancers are divided into five stages:
- Stage 0: In this earliest stage, it is usually determined after removal of a polyp during a colonoscopy that cancer cells were already present in its mucosa. Further therapy is usually not necessary here.
- Stage I: Here, too, a small tumor in the early stage is usually discovered in the course of a colonoscopy and removed in a small surgical procedure using an endoscope. At this stage, the colon cancer is well curable.
- Stage II: Surgery to remove the tumor is usually necessary. For colon cancer, this usually ends the treatment, while for rectal cancer, additional radiation and chemotherapy is often performed.
- Stage III: At this stage, the colon cancer has already spread to the lymph nodes. In addition to surgery, chemotherapy and or radiation therapy is necessary.
- Stage IV: The tumor has already metastasized to other organs. By means of drug treatment and surgery, these are treated.
Complications of colorectal cancer
Especially with very fast-growing tumors, there is a risk of intestinal obstruction (ileus), which must be immediately repaired surgically. Metastases can prevent the outflow of bile and lead to liver failure.
Surgery for colorectal cancer
The centerpiece in the treatment of colorectal cancer is still surgery. When removing the affected section of colon, the surgeon tries to preserve the anal sphincter to maintain normal defecation. However, this is not always possible, especially if the cancer is located in the lower section of the colon or has already spread extensively. In this case, the end of the intestine is passed through the abdominal wall to the outside via an artificial intestinal outlet (colostomy). The metastases (mostly in the liver) are also surgically removed if possible. In recent years, overheating (hyperthermia) by microwaves or the introduction of chemical agents directly into the metastasis have been added as further therapy options. The combination of surgery followed by chemotherapy and/or radiation can improve the prognosis.There is hope that in the future a cure will be possible even for extensive disease findings.
Palliative therapy
If surgery is not an option, attempts are made to relieve symptoms (palliative therapy). This is done by maintaining intestinal patency (strictures can be irradiated with laser if necessary) and by the use of chemotherapy and x-rays.
The right diet for prevention
Various substances in the diet are said to have an intestinal protective function, such as vitamins (vitamin E, C, folic acid) and acetylsalicylic acid. However, the studies produce partly contradictory results – in some cases, even more cancer cases were observed with high-dose vitamin supplements. Instead of taking dietary supplements, it is therefore more sensible to ensure a varied and balanced diet: low in fat, high in carbohydrates and fiber, lots of vegetables and fruits, plenty of fluids, ideally green tea. This guarantees an adequate vitamin intake without the risk of overdosing and a fast stool passage due to plenty of fiber. Exercise is also said to prevent – at least it supports bowel activity and helps against obesity.
Cancer screening and colonoscopy
Many experts recommend colonoscopy at regular intervals (every three years) in addition to the annual rectal examination from the age of 50 as part of early detection. Regular examination of the stool for blood should also be part of the cancer screening. Successfully treated patients must undergo a precisely specified tumor follow-up, which consists, among other things, of the detection of CEA. These measures allow early detection and treatment of cancer recurrence (relapse).
