What is Colorectal Cancer
Colorectal cancer includes tumors that affect a part of the large intestine (the colon) and the rectum (the end of the intestine, located before the anus). When diagnosed early, it is usually treatable and, in many cases, curable. This is generally possible when it has not spread to other organs (in the so-called metastasis).
Most of these tumors start from the appearance of polyps, which are benign lesions that can grow on the inner wall of the large intestine.
Colorectal Cancer: Statistics, Incidence, and Trends
Rectal cancer itself also begins in the lining cells and starts as a polyp. Its incidence is approximately 29% among intestinal tumors. It is worth detailing that the rectum is the portion of the large intestine delimited inferiorly by the pectinate line. The low rectum is up to 5 cm from the anal verge, the middle rectum is between 5 and 10 cm from the anal verge, and the high rectum is between 10 and 15 cm from the anal verge.
Data from the latest global estimate indicate that 1 million new cases of colon and rectal cancer were reported in men, making it the third most common tumor among all male cancers, with an estimated risk of 26.6/100,000. For women, this number was slightly lower, with the registration of 800,000 new cases, making it the second most frequent tumor, with an incidence rate of 21.8/100,000.
Colorectal Cancer Statistics in Brazil
In Brazil, it is estimated that between 2018 and 2019, 36,360 new cases of colorectal cancer have emerged, with 17,380 in men and 18,980 in women. These values correspond to a risk of 16.83 new cases per 100,000 men and 17.9 per 100,000 women in our country.
In terms of mortality, according to the INCA (National Cancer Institute), in 2017, 9,207 deaths from colon and rectal cancer (9.12/100,000) were observed in men and 9,660 (9.33/100,000) in women in Brazil.
The incidence of colorectal cancer has a significant increase after the age of 50 and continues to increase with advancing age, although the number of cases has recently increased in younger patients.
Risk Factors for Rectal Cancer
The risk factors for rectal cancer are closely related to dietary and lifestyle habits and previous health conditions. Among them, the following stand out:
- Diets high in red meat, processed meat, and meats exposed to high heat;
- Low-fiber diets (fruits, vegetables, and vegetables);
- Sedentary lifestyle (as obesity is a risk factor, and maintaining regular exercise helps prevent it);
- Chronic inflammatory bowel diseases (such as ulcerative colitis and Crohn’s disease);
- Family history of colorectal cancer; and
- Family syndromes (especially Lynch syndrome and familial adenomatous polyposis – FAP)
Subtypes of Colorectal Cancer
The vast majority of colorectal tumors are classified as adenocarcinomas. These cancers begin in cells that secrete mucus to lubricate the inside of the colon and rectum and have some subtypes, such as signet ring cell adenocarcinoma and mucinous.
Other types of tumors that can start in the colon and rectum include:
- Carcinoid tumors;
- Gastrointestinal stromal tumor (GIST);
- Lymphomas; and
- Sarcomas.
Symptoms of Colorectal Cancer
Colorectal cancer can be a silent disease and may not cause immediate symptoms. But when present, they may include:
- Changes in bowel habits, such as diarrhea, constipation, or narrowing of stools, lasting for several days;
- Even after bowel movements, there is no feeling of relief, as if not all fecal content has been eliminated (especially suggestive symptom in cases of rectal cancer);
- Rectal bleeding (the blood is usually bright red);
- Presence of blood in the stool, making its color dark brown or black;
- Abdominal cramps or pain;
- Feeling of fatigue and weakness; and
- Unexplained weight loss.
It’s important to note that many of these symptoms can be caused by conditions other than colorectal cancer, such as infection, hemorrhoids, or Irritable Bowel Syndrome. That’s why it’s important that at the first sign of abnormality, you seek medical evaluation.
Diagnosis of Colorectal Cancer
The first step in diagnosing colorectal cancer is to trace the patient’s medical history to identify possible risk factors.
The physical exam may include palpation of the abdomen to look for abnormalities, such as masses or enlarged organs. Additionally, a digital rectal exam may be performed, where the doctor inserts a finger (protected by a lubricated glove) into the rectum to assess for any abnormal areas.
Other tests may be requested in the diagnostic process of colorectal cancer. They are:
- Stool test;
- Blood tests;
- Colonoscopy;
- Biopsy; and
- Imaging tests (X-ray, ultrasound, magnetic resonance imaging, computed tomography, and PET scan).
In the diagnosis, the staging of colorectal cancer is also determined, that is, the phase in which the tumor is classified. It is very useful to assist the doctor in making decisions about treatment. In colorectal cancer, there are four stages:
- Stage I – tumor confined to the mucosa (IA) or the muscular layer (IB) of the colon or rectum and without involvement of lymph nodes (ganglia);
- Stage II – tumor confined to the serosa that covers the colon or rectum (IIA) or that has reached neighboring organs (IIB), but without involvement of lymph nodes (ganglia);
- Stage III – involvement of lymph nodes near the colon or rectum; and
- Stage IV – involvement of distant organs.
Treatment for colorectal cancer
The doctor and a multidisciplinary team determine treatment options according to the diagnosis of colorectal cancer.
The main approaches adopted in the management of colorectal cancer are:
- Local treatments – treat the tumor without affecting the rest of the body. They are more indicated in the early stages of the disease (in smaller tumors that have not yet spread/metastasized), but can also be used in other situations. The main types used in colorectal cancer include surgery, ablation, embolization, and radiation therapy;
- Systemic treatments – through the use of oral drugs (tablets) or intravenous drugs (in the vein), which are applied directly into the bloodstream. Depending on the type of colorectal cancer, chemotherapy, targeted therapies, and/or immunotherapy may be used.
Prevention of colorectal cancer
Primary prevention of colorectal cancer includes measures to reduce the risk of developing the disease, such as:
- Adopting a diet rich in fiber, fruits, and vegetables;
- Reducing the consumption of red meat and animal fat;
- Engaging in physical activities, as sedentary behavior increases the risk of developing the disease;
- Maintaining a healthy weight (remembering that obesity is a risk factor for this cancer); and
- Avoiding smoking and the intake of alcoholic beverages.
