Colon cancer occurs due to the uncontrolled proliferation of mucosal cells found in the colon. Generally, this type of cancer is divided into colon cancer and rectal cancer, the latter affecting the last part of the intestine.
This type of cancer usually strikes after the age of 50 and, as reported by AIRC, in Western countries it is the second most common malignant tumor after breast cancer in women, and the third after lung and prostate cancer in men.
Common symptoms of colon cancer
The most common and early symptoms of colorectal cancer are:
In addition to these very common symptoms, there are rarer signs such as:
Obviously, in case of strange symptoms and constant fatigue for several weeks it is advisable to always consult your doctor for a more in-depth check-up in order to identify the causes of the discomfort.
Risk factors
Colon cancer risk factors are closely linked to diet and genetic factors.
Nutritional factors
According to the AIRC, diet has a strong impact on the risk of developing colon cancer; in fact, a diet high in fat and animal protein but low in fiber is associated with an increase in intestinal tumors. In addition to nutrition, a sedentary lifestyle and obesity also have an impact. (Read also: Obesity: there are 2 billion obese people in the world)
Genetic factors
The chances of contracting cancer increase in case of genetic predisposition. Even with regards to colorectal cancer, in fact, if cases of tumors have occurred in the family of origin, the probability of transmitting the malignant gene to the offspring is as high as 50 percent.
Non-hereditary factors
The possibility of contracting colon cancer is also affected by non-hereditary factors such as:
Prevention
As with all other tumors, prevention is essential; in fact, the chances of recovery increase if the disease is identified and diagnosed at its initial stage. In Italy, for example, for colorectal cancer all people between the ages of 50 and 69 can undergo a free screening program for the early diagnosis of colorectal cancer.
The role of polyps and the importance of screening
Colorectal cancer almost always develops from adenomatous polyps, benign formations that grow on the intestinal mucosa. The good news is that the process of transformation from a benign polyp to a malignant tumor is very slow: on average it takes between 7 and 15 years.
This long time window represents a precious opportunity for prevention. Through screening it is in fact possible to identify and remove polyps before they degenerate into cancerous forms, thus stopping the development of the disease in its tracks.
Because polyps are detectable
Polyps have two characteristics that make their detection easier:
Screening tests available
Based on these characteristics, the screening tests currently used in national programs are:
Testing for fecal occult blood (SOF)
The fecal occult blood test is the first level test offered free of charge by the National Health System. It involves looking for microscopic traces of blood in a stool sample, which may indicate the presence of bleeding polyps. This test is recommended every two years for people between the ages of 50 and 69, with some regions having extended screening up to age 74.
On average, around 5 out of 100 people test positive, but this does not automatically mean you have a polyp: traces of blood can result from hemorrhoids or small lesions caused by constipation. The test also has limitations: it may happen that a polyp is present but does not bleed on the day of the test, and this is why it must be repeated regularly. Despite these limitations, it remains an excellent screening test, made even more effective by modern analysis techniques that no longer require food restrictions.
When the test is positive, the protocol involves proceeding with a colonoscopy to check for the presence of polyps and, if necessary, remove them in the same session.
Rectosigmoidoscopy
Considering that approximately 70% of colorectal cancers develop in the final part of the intestine (sigmoid and rectum), some screening programs use rectosigmoidoscopy instead of testing for occult blood. This test is similar to a colonoscopy but only explores the last 30 centimeters of the intestine, making it less invasive.
Rectosigmoidoscopy has several advantages: it requires less troublesome preparation, takes about half the time compared to a complete colonoscopy, has greater diagnostic efficacy than the occult blood test and allows any identified polyps to be immediately removed. It is carried out only once in a lifetime, between the ages of 58 and 60, and if it is negative it offers protection for more than 10 years thanks to the slow development times of this type of tumor.
The main limitation of this test is the impossibility of identifying polyps and tumors that develop in the upper part of the colorectum. For this reason, when polyps measuring 1 centimeter or larger, or smaller polyps but with particular characteristics, are detected, a complete colonoscopy is still recommended.
Colonoscopy
Complete colonoscopy is used as a second-level test after a positive occult blood test result. During the exam, a colonoscope (flexible instrument with light and camera) is introduced into the anus to observe the mucosa of the entire colon. The doctor can take samples of any lesions found, which are then analyzed with histological examination.
Despite its very high diagnostic benefits, colonoscopy is not used as a first-level test in screening programs for various reasons. First of all, due to its invasiveness, it is difficult to accept by a healthy population: it causes discomfort both during intestinal preparation and during execution. Furthermore, although rarely, it presents some risks such as the possibility of contracting infections. Finally, the times and methods of execution make it an expensive test for both patients and the healthcare service.
Virtual colonoscopy
Introduced in 1997, virtual colonoscopy simulates traditional colonoscopy through a CT scan that provides a three-dimensional view of the internal wall of the intestine. Before the exam, air is introduced through a flexible tube into the rectal ampulla. This technique has now achieved high levels of diagnostic accuracy.
Compared to the occult blood test, virtual colonoscopy is more immediate and accurate, allowing the diagnosis to be made earlier. Compared to traditional colonoscopy, it does not require the intake of strong laxatives and could therefore be better accepted by the population.
However, it has significant limitations. Unlike traditional colonoscopy, it uses ionizing radiation which constitutes an oncological risk factor. Furthermore, once a polyp has been identified, it is not possible to eliminate it in the same session but it is necessary to resort to the traditional examination, increasing both the inconvenience for the patient and the costs. The real effectiveness of the test is still little known, in particular its ability to detect small polyps is unclear.
For these reasons, despite being a safe procedure used in the prevention of colorectal cancer, virtual colonoscopy is not part of organized screening programs, except in particular cases such as in-depth analysis when the traditional examination is incomplete or has limitations in execution for the patient.
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