What is it?
Colorectal cancer is an uncontrolled growth of cells in the colon and / or rectum. Most colorectal cancers start as a growth on the inner lining of the colon or rectum, which is called a polyp. Some types of polyps can become cancer over time (usually many years), but not all polyps become cancer.
Colorectal tumors can originate in each of the three layers of the colon: mucosa, muscle, and serous.
This type of cancer is one of the most common worldwide and also one of the easiest to diagnose. Furthermore, cure rates are high if detected early and take a long time to develop.
Colon cancer can grow in three ways:
Local growth: In this case the tumor deeply invades all the layers of the wall of the digestive tract. First, the malignant tumor grows from the mucosa, expands through the serosa, and reaches the muscle layers.
Lymphatic spread: When the tumor deepens in the wall of the intestine, it can reach other organs using the network of lymphatic vessels that allow access to multiple lymph node regions. One of the characteristics of this diffusion is that it is carried out in an orderly manner, reaching the nearby nodes first until reaching the most distant ones.
Hematogenous spread: Here the tumor is served from the bloodstream to spread cancer cells to the liver, lungs, bones and brain, mainly.
According to data from the Spanish Association against Cancer, colorectal cancer is the most frequently diagnosed in the Spanish population when the incidence in both sexes is added, with 37,172 cases detected in 2018.
When data is disaggregated, the most frequently diagnosed cancer in men is prostate cancer and, in women, breast cancer.
As for mortality, it is responsible for more than 15,500 deaths a year.
The main risk factors related to this disease are the following:
Age: Most cases of colon cancer are located in people between 65 and 75 years old and people between 50 and 65 are considered intermediate risk. The cases that are diagnosed before the age of 35-40 years are usually due to the fact that the patient has a genetic predisposition to suffer this pathology.
Diet: Colon cancer appears to be associated with diets high in fat and low in fiber. In this regard, numerous investigations are currently underway.
Heredity: Genetics plays an important role in colon cancer, since there is a possibility that it will be transmitted hereditary and predispose the person to suffer the disease. However, this can be detected and allow cancer to be treated early.
Medical history: It has been shown that those who have a greater predisposition to suffer from this disease are people who have or have had polyps (benign growth) of the colon or rectum, ulcerative colitis (inflammatory bowel disease), cancer of the breast, uterus or ovaries.
First or second degree relatives who have also had colon cancer.
Lifestyle: There are certain factors that depend on lifestyle and predispose to the appearance of colon cancer, such as obesity, sedentary lifestyle, smoking and excessive alcohol consumption.
In people with some type of inflammatory bowel disease, such as ulcerative colitis or Crohn’s disease, the risk of developing the disease increases.
Colorectal cancer has a long evolution and its symptoms can vary depending on the location of the tumor in the large intestine. The most frequent complaints appear in the advanced phase of the disease. However, these symptoms are not exclusive to colon cancer and can occur in other pathologies such as hemorrhoids or certain digestive disorders. Specialists recommend going to the doctor as soon as they appear to facilitate the diagnosis being made properly. The most common are:
Changes in bowel rhythm
Patients who have colon cancer may, in some cases, have diarrhea and, in others, constipation. The second possibility is common in those who had a normal intestinal rhythm prior to the disease. However, most often the patient suffers from periods of constipation combined with periods of diarrhea.
Blood in the stool
The most common symptom of this malignant tumor is that the patient has blood in the stool. The color of the blood can be red or black. The presence of red blood occurs mainly when the person presents tumors of the most distal part of the colon and rectum. In the case of black blood, this color appears because the blood is digested and comes from closer sections of the colon giving rise to black bundles known as melena. If this symptom is not diagnosed early and the patient does not receive adequate treatment, it can worsen and lead to anemia. In these cases, the patient may suffer dizziness, tiredness or have the sensation of being short of breath, among other symptoms.
On the other hand, the patient can detect that his stools change in size and are narrower. This occurs because the intestine is narrowing.
If the tumors are located in the distal part of the colon, the patient may also have the feeling that the stool is not complete and that the evacuation is incomplete.
Abdominal pain or discomfort
Abdominal pain and discomfort are usually very common. This is because the tumor partially obstructs the intestinal tube, causing pain and a colic-like condition. In some cases the closure of the tube can be completed and an intestinal obstruction occurs, in these situations it is necessary for the patient to receive urgent surgical medical attention.
Weight loss without apparent cause, loss of appetite and constant tiredness
Like other diseases related to the stomach, colon cancer, especially when it is in an advanced state, presents these symptoms.
There are risk factors for all cancers that make people who are exposed to them more likely to develop a malignant tumor.
Colorectal cancer research has shown that in some types, tumors originate from polyps (small benign lumps). Early detection and removal of these polyps can help prevent the disease from developing.
Another cause of the appearance of colon cancer is the person’s genetic predisposition. This is due to various alterations in certain genes, therefore, individuals with relatives who have or have had this pathology should go to medical examinations periodically.
There are different syndromes that predispose the malignant tumor to appear. The most common are two:
Familial colonic polyposis
This syndrome only causes 1 percent of colon cancers. Familial colonic polyposis appears during adolescence causing multiple polyps in the rectum and colon. The cause of the appearance is the mutation of the APC gene, which is transmitted from parent to child. This gene can be inherited by both girls and boys.
Hereditary nonpolyposis colorectal cancer
This type of cancer accounts for between 3 and 5 percent of tumors of the rectum and colon. The main difference from the previous syndrome is that patients do not have polyps.
Some unhealthy habits can also influence the appearance of the disease, so following the following tips can be very beneficial:
Do not abuse alcohol or tobacco: Tobacco increases the risk of developing polyps that can be precursors of the disease. Regarding alcohol, its consumption favors the growth of the cells of the lining of the colon. This growth gives rise to polyps.
Control overweight: Obesity and excess calories in the diet should be avoided. Regular physical exercise contributes to a sedentary lifestyle and the appearance of the disease is favored.
Diet: Specialists advise to follow a balanced diet and recommend the following guidelines.
Do not abuse high fat foods.
Reduce the consumption of fats so that they do not exceed 20 percent of the total calories in the diet, preferably consuming monounsaturated fats (olive oil) and polyunsaturated fats (fish oil).
Reduce the intake of red meat.
Increase the fish and chicken consumption.
Incorporate fiber-rich foods into the diet since taking an amount of fiber of at least 25 grams daily, in the form of cereals and whole wheat bread, prevents the appearance of the tumor.
Increase the intake of fruits and vegetables. Especially cauliflower, Brussels sprouts, broccoli, and legumes.
In 90-95 percent of cases, adenocarcinoma is the most common type of colon cancer. This is located in the mucosa that lines the inside of the colon and rectum. The least frequent types are the following:
Lymphoma: Cancer of the defense cells of the intestine and stomach.
Sarcoma: This tumor arises in the muscular layer of the digestive tract.
Carcinoid tumors: It occurs in the hormone-producing cells of the digestive system.
One of the main advantages of colon cancer is that it is one of the few types that can be diagnosed before the person has symptoms and even before the polyps turn into cancer.
The most reliable screening test is a fecal occult blood test that checks for blood or not. The patient obtains the sample at home and delivers it to his health center to be analyzed and interpreted by a specialist. This test is recommended, as a general rule, every two years from the age of 50.
If positive, then a colonoscopy will be performed to see the source of the bleeding. This test is used to detect and remove polyps in the same act, in order to prevent the tumor from developing and, where appropriate, malignant.
Once there is a suspicion that there may be an injury to the colon, the doctor should prepare a medical history, perform a physical examination and a digital rectal examination. Several techniques are used to detect colon cancer:
Rectal examination: It is a physical examination that the doctor performs by inserting a finger into the anus to detect abnormalities in the lower part of the digestive system, such as blood, abnormal lumps or if the patient feels pain.
Sigmoidoscopy: It is an exploration that consists of introducing through the anus a tube that transmits light and image, and which is called an endoscope. With it you can examine the rectum and the end of the colon (about 60 cm), and detect some of the polyps that may be there.
Colonoscopy: It is an examination similar to sigmoidoscopy, but the tube used is longer and allows the entire colon to be covered. Facilitates tissue sampling (biopsy) in areas where a tumor is suspected, and then a microscopic study is performed. It is normally performed with sedation and the risk of complications arising is very low.
Genetic study: If there is a family history or the possibility of hereditary cancer is suspected, it is advisable to carry out a genetic study to detect abnormalities. If there are genetic alterations in the family, colon and rectal examinations should be started at an early age (20 years) and continued periodically.
Barium enema with double contrast: It consists of a series of x-rays of the colon and rectum that are taken after the patient has had an enema (laxative) with a white calcareous solution that contains barium to show radiologically in detail the interior of the colon and rectum.
In recent years, the technique known as liquid biopsy is being investigated intensively, which can be especially useful in colon cancer. This is a test done on a blood sample to look for cancer cells that are circulating in the blood or DNA fragments of tumor cells that are circulating in the blood. When its use is standardized, it can be used to detect cancer early, plan treatment or determine its effectiveness, among other things.