Onset, symptoms, diagnosis, therapies
and prevention of one of the most widespread cancers in the world
Anatomy: understanding the intestine
Colorectal cancer is an oncological condition that affects the colon and rectum, two essential parts of the gastrointestinal system or digestive system. These two anatomical segments are part of the intestine, the organ that plays a crucial role in digestion, nutrient absorption, and waste elimination. The small intestine looks like a long, sinuous tube that extends for about 7 meters from the end of the stomach to the anus and is divided into two main anatomical sections:
- Small intestine: the upper part of the intestine, further divided into three sections: duodenum, jejunum, and ileum. The small intestine is responsible for the majority of nutrient absorption from the food we eat. Here, the final digestion of food occurs, and essential nutrients such as proteins, carbohydrates, fats, vitamins, and minerals are absorbed through the walls of the small intestine and enter the bloodstream for use by the body.
- Large intestine: the lower part of the intestine, consisting of three main sections: cecum, colon, and rectum. The large intestine, approximately 2 meters long, is primarily involved in absorbing water and minerals from undigested food residues coming from the small intestine. This process contributes to making the feces more solid and ready for elimination. The colon, in particular, is responsible for absorbing water, salts, and synthesizing, thanks to the human microbiota present here, some essential fat-soluble vitamins from waste substances before they are eliminated. The rectum, on the other hand, is the terminal part located just before the anus, and its crucial function is to temporarily store feces before they are expelled from the body through the process of intestinal evacuation. The rectum is equipped with muscles that allow its contents to be released in a controlled manner.
Incidence and risk factors
Colorectal cancer is one of the most common types of cancer worldwide, especially according to estimates provided by the Ministry of Health in the “Cancer Numbers 2022“ edition (a project born from collaboration between AIOM – Italian Association of Medical Oncology, AIRTUM – Italian Association of Cancer Registries, ONS – National Screening Observatory, and other important associations). In 2022, approximately 48,100 new diagnoses of colorectal cancer were estimated in Italy, with 26,000 new cases in males and 22,100 in females. The disease, relatively rare before the age of 40, is more prevalent in people between the ages of 60 and 75.
Age is one of the main risk factors for the development of colorectal cancer, along with:
- Genetic predisposition (it is possible to inherit a predisposition to colorectal cancer if diseases such as polyposis and colorectal carcinomas have occurred in the family).
- Unhealthy eating habits (a diet high in fats and animal proteins but low in fiber is associated with an increased risk of intestinal tumors. Diets rich in fiber, characterized by a high consumption of fruits and vegetables, seem to have a protective role).
- Smoking and alcohol abuse.
- Obesity and a sedentary lifestyle.
- Intestinal polyps (a past clinical history of colon polyps or previous colorectal cancer).
- Inflammatory bowel diseases (such as ulcerative colitis and Crohn’s disease).
Onset of colorectal cancer
Most colorectal tumors result from the malignant transformation of polyps, small abnormal tissue growths that develop on the intestinal mucosa. Among various types, adenomatous polyps constitute precancerous lesions, and a small percentage of them can transform into malignant neoplasms through a process known as the “adenoma-carcinoma sequence”. The likelihood that a colon polyp evolves into an invasive form of cancer depends on various factors:
- increase in the size of the polyp;
- presence of multiple polyps;
- presence of dysplasia areas (an abnormal appearance of cells observed under the microscope).
Symptoms of colorectal cancer
Symptoms of colorectal cancer can vary from person to person and depend on the stage of the disease, influenced by factors such as the tumor’s location, its extension, and the presence or absence of obstructions or bleeding. Some individuals may not show any symptoms in the early stages, while others may experience evident signs. Here are some of the most common symptoms associated with colorectal cancer:
- Changes in bowel movements, which may include diarrhea, constipation, or a feeling of incomplete bowel emptying after evacuation.
- Rectal bleeding or the presence of blood in the stool.
- Abdominal pain and/or a sensation of abdominal bloating.
- Persistent fatigue and weakness.
- Significant and involuntary weight loss.
- Iron deficiency anemia.
Diagnosis e tests
The diagnosis of colorectal cancer begins with a comprehensive medical evaluation and a series of exams. Foremost among them is a colonoscopy, which allows doctors to directly examine the inside of the colon and rectum for anomalies, polyps, or tumors and, if necessary, perform a biopsy. Other screening tests include blood tests (checking for the carcinoembryonic antigen tumor marker), urine and stool tests, ultrasound, computed tomography (CT), and magnetic resonance imaging. Early diagnosis is crucial for effective management of colorectal cancer, significantly increasing the chances of treatment success and improving the patient’s prognosis. Therefore, it is important to participate in screening programs recommended by healthcare professionals and consult a doctor in case of symptoms or risk factors.
TNM staging system
The TNM system is the most widely used method to assess the extent of colorectal cancer. “TNM” represents the three main components considered in staging:
- T (Tumor): indicates the size and extent of the primary tumor in the colon or rectum. The degree of invasion through the organ walls and the presence of involvement of surrounding tissues are evaluated.
- N (Node): refers to the presence and extent of involvement of regional lymph nodes by the tumor. The identification of positive lymph nodes indicates that cancer has spread to the lymph nodes, which can affect prognosis.
- M (Metastasis): considers the presence or absence of metastasis, i.e., the spread of the tumor to distant organs or tissues, such as the liver or lungs.
Combining these three components assigns a “stage” to the tumor, usually indicated as stage 0 (in situ tumor) up to stage IV (advanced metastatic tumor). Staging helps determine the most appropriate treatment and provides crucial information about the prognosis of patients with colorectal cancer.
Treatment options to counter colorectal cancer
Treatment options for colorectal cancer depend on the stage of the disease and the overall health of the patient. Surgery is often the first step and may involve the removal of part of the affected colon or rectum. In some cases, emergency intervention may be necessary to address obstructions or bleeding.
Chemotherapy is also widely used as a counteractive treatment. It can be neoadjuvant (performed before surgery) or adjuvant (after surgery). The primary goal of neoadjuvant therapy is to reduce the size of the tumor before proceeding with surgical removal. The aim of adjuvant therapy is to destroy any residual cancer cells and prevent recurrences. There are many oncology drugs active in treating colorectal cancer, and they can be used alone or usually in combination. Today, numerous targeted therapies, called smart drugs, biological drugs, or molecular-targeted drugs, are available. Molecular analysis plays a prominent role in choosing the most suitable therapy to counter colorectal cancer by evaluating possible genetic mutations.
Radiation therapy is also used in the treatment of colorectal cancer, as it can induce necrosis – the death – of tumor cells through the use of high-energy radiation called ionizing radiation.
The contents of this page are for informational use only and in no case should they replace the opinion, diagnosis or treatment prescribed by your doctor. The response to the same treatment can vary from one patient to another. Always consult with your doctor on any information relating to diagnosis and treatment and scrupulously follow his instructions.