Colorectal cancer is a cancerous disease of the large intestine. By the way it is diagnosed and treated we must distinguish colon cancer proper (2/3 of colorectal cancers) and rectal cancer. By far the most frequent histological type is adenocarcinoma (97%). It is the second most frequent malignant tumor in developed countries in both sexes and the first cause of death by tumor. In men, it is the second cause of death after lung cancer and its prevalence is 26,500 cases per year.
What symptoms do patients suffering from this pathology present?
- Colon cancer most commonly produces occult blood loss in the stool, as it is of a small amount, although, if it is prolonged over time, it could produce anemia.
- One of the most frequent symptoms of colorectal cancer is rectorrhagia, or emission of blood from the anus, which can be mixed with stool (hematochezia) or independently, rectorrhagia itself.
- Another possible symptom is the appearance of obstructive symptoms, such as a change in bowel habit, abdominal distension and even nausea and vomiting when the obstruction is definitively established. Evidently this happens when the tumor reaches a certain size and occurs fundamentally in those of the left colon and sigma.
- On occasions, this sensation of distension and fullness may lead to a reduction in food intake and, therefore, to weight loss. When this occurs in a tumor located in the rectum, it may be accompanied by rectal tenesmus, which is defined as the sensation of incomplete evacuation and a sustained sensation of the need to defecate; this occurs due to the occupation of the rectal lumen by the tumor, although this may be a non-specific symptom. Tumors of the right colon usually produce only blood loss with the stool, leading to anemia which, when studied by colonoscopy, is diagnosed.
What could be the causes?
There is experimental, epidemiological and clinical evidence that diet influences the development of colorectal cancer. The diet contains multiple mutagens and carcinogens that can derive from natural chemical compounds and heterocyclic amines derived from the cooking of food.
Another factor that has been shown to be related to colorectal cancer is the high consumption of red meat, due to its nitrosamine content. The consumption of large amounts of fiber in the diet is considered a protective factor against colorectal cancer, by increasing the transit speed of these nitrosamines and thus decreasing the contact time of these substances with the colonic mucosa. Likewise, calcium, selenium and other micronutrients such as phenols, indoles, vitamins A, C and E and carotenoids, contained in small amounts in water, grains, fruits and vegetables, reduce the risk of colorectal cancer. Likewise, the relationship between colorectal cancer and alcohol consumption has been described, and it doubles the risk in subjects with daily consumption.
Another of the carcinogenetic factors in these tumors is tobacco consumption, which is estimated to be responsible for the appearance of up to 12% of colorectal tumors. Obesity is a recognized risk factor, while physical activity seems to reduce the incidence of colon cancer, especially of the right colon, with a relative risk double in sedentary subjects. Finally, we can find some colorectal cancers considered to be hereditary, whether or not associated with polyposis.
What type of patients suffer from colon cancer to a greater extent?
75% of colorectal cancers develop in patients with no risk factors, 15% in patients at intermediate risk (family history of colorectal cancer) and 10% in patients at high risk (Lynch syndrome or HnPCC, familial polyposis, ulcerative rectocolitis). For this reason, early detection campaigns are currently being implemented in different geographical areas by means of the fecal occult blood test. According to the Spanish Association of Surgeons, the risk of colorectal cancer is established by family history according to the table published in the ACS guidelines:
HNPCC: non-hereditary polyposis colorectal cancer.
FAP: familial adenomatous polyposis.
In people without risk factors, one of the following screening schemes is recommended from the age of 50 years: fecal occult blood annually, sigmoidoscopy every 5 years, double contrast enema every 5-10 years, colonoscopy every 10 years.
What is the treatment followed to combat it?
The treatment of choice for colorectal cancer is surgical, however, depending on the location and stage of the tumor, it may be necessary to add adjuvant chemotherapy and, in the case of rectal cancer, it may be necessary (depending on the location and preoperative stage determined by MRI) to perform neoadjuvant chemotherapy and radiotherapy (before surgery) and complete it with adjuvant treatment after surgery.
The surgical treatment of choice for colon cancer and upper and middle third rectal cancer is the laparoscopic approach, always ensuring a correct excision of the mesocolon or mesorectum, where all the lymph nodes are located, considered one of the main routes of dissemination of these tumors.
There is currently controversy as to whether the approach to lower third rectal cancer should be by conventional open or laparoscopic approach, although there are currently many surgical teams that advocate the conventional laparoscopic approach or the “down to up” technique with good results from the oncologic point of view. Sometimes it is necessary to remove the entire rectum together with the sphincteric apparatus (Milles abdominoperineal amputation), and in these cases the patient must remain with a colostomy for life. A different situation, however, is when performing rectal surgery, the surgeon decides to perform a protective ileostomy (opening an intestinal loop to the outside for stool or intestinal fluid emission) in order to temporarily dysfunctionalize the operated area (in particular the anastomosis) until adequate healing is verified, at which time the ileostomy will be closed to restore transit, this ileostomy being a temporary condition.