General and more comprehensive text about cancer diseases, their behavior, causes and treatment can be found here.
Colorectal cancer is one of the most common malignant diseases in the developed countries. It is closely related to lifestyle, its advanced stages have a poor prognosis, but on the other hand, when found in time, it can be very easily treated.
There are many inherited genetic conditions that may combine with outer risk factors. The age is a clear risk factor as the majority of cases occur in patients above 50 years of age. Male sex is riskier. Colorectal tumor occurs more frequently in people with colorectal cancer in their family history. In addition, there are many genetically inherited disorders and syndromes that are clearly related to high risk of colorectal cancer, for example the known familial adenomatous polyposis, Lynch syndrome, Gardner's syndrome and Turcot syndrome.
The diet and the general lifestyle also have a large influence on the disease. It is assumed that excessive intake of fats, low intake of dietary fiber and the lack of physical exercise increase the risk of the tumor. The dietary fiber is an important protective factor as it prevents constipation “cleans” the intestines and prevents local formation of potentially carcinogenic substances. Other risk factors include smoking and chronic alcoholism.
Scheme - Progression of an intestinal polyp into colorectal cancer
The tumor is initially asymptomatic. It may mildly bleed and cause occurrence of bright red blood in stool. However, there is usually present only a trace amount of blood present, which can not be seen by the naked eye. Chronic blood loss may cause anemia due to iron deficiency and this can manifest with the anemic syndrome. Tumors located in the left colon cause frequently alternating constipation and diarrhea and tumors in the rectum may cause pain during defecation and presence of mucus in stool. Advanced disease may be related to weight loss, loss of appetite, night sweats, liver enlargement (due to liver metastases) and other symptoms. Large tumor mass may narrow or even obstruct the large intestine leading to symptoms of intestinal obstruction (ileus).
Diagnosis and prevention
The best primary prevention is healthy lifestyle with adequate physical activity and high intake of dietary fiber. Smoking and excessive alcohol drinking are not advised. Because the colorectal cancer is very frequent, yet well-treatable in its early stages, many countries have a screening program dedicated to actively diagnose early stages of the tumor in the whole population. The screening programs are different in various countries, but usually they include the fecal occult blood test (FOBT) and colonoscopy.
The fecal occult blood test is an ideal screening examination. There are more types of the tests, but their purpose is the same – to detect trace amounts of blood from stool samples. Modern tests are not only able to detect the blood, but also predict the risk of cancer (by measuring the precise amount of blood). Positive finding does not confirm the tumor, but it is a reason to perform a diagnostic colonoscopy.
Colonoscopy is the best diagnostic method of colorectal cancer. It can find the tumor tissue, determine its location, visualize the tissue by a video-camera and take samples for histological examination.
The local extent of the tumor, affection of local lymph nodes and presence of distant metastases may be examined by imaging methods such as abdominal ultrasound and computed tomography. Some types of rectal cancer may be diagnosed by endosonography and magnetic resonance imaging (evaluation of the depth of the tumor process).
The therapy depends on the stage, where the tumor has been diagnosed. Local small tumors can be treated endoscopically; malignant polyps can be removed by polypectomy. More advanced tumors are treated surgically by removal of the tumor, part of the large intestine and eventually even the local lymph nodes. Sometimes, the surgeons create a temporary colostomy. Chemotherapy and radiotherapy are rather supportive methods used in combination with the surgery. Some types of the tumor may be treated by biological therapy, which uses special substances blocking the tumor from local production of its own blood vessels. Without the blood supply, the tumor cells do not have enough nutrients and the tumor growth is disrupted.