27 February 2019 Cancers that develop in the colon or rectum, due to their numerous common characteristics, are often referred to as colorectal cancer. Although one of the easiest cancers to prevent , colorectal cancer is the second-most deadly cancer in the Western world. How does colorectal cancer develop? Most colorectal cancers develop from a cell or a group of cells on the inner lining of the intestinal wall (mucous). These cells multiply and organise themselves into a small, non-cancerous tumour known as a polyp . Polyps appear as raised or projected areas on the internal lining of the abdominal wall. As it grows, a polyp can turn into a cancer . This means it has the ability to invade neighbouring tissues. This “invasion” occurs either through the intestinal wall or at a distance, whereby other parts of the body are affected via the lymphatic and/or blood circulation. The transformation of a benign polyp into a malignant tumour (or cancer) appears to be the result of inherited or spontaneous changes or mutations of the genes controlling the cells. Early detection and removal of polyps can substantially reduce the likelihood of the disease occurring. Who is at risk Age is one of the main risk factors for colorectal cancer: More than 90% of these tumours occur in people over the age of 40; The majority are diagnosed between the ages of 50 and 70. As well as age, there are other factors associated with an increased risk of colorectal cancer: Personal history of breast, uterine or ovarian cancer; Inflammatory bowel disease (ulcerative colitis or Crohn’s disease); Family or personal history of polyps or bowel cancer; Smoking. Consumption of large amounts of animal fat and low levels of fibre have also been associated with a greater probability of bowel cancer, although opinions differ on this point. Colorectal cancer: what are the symptoms? The most common symptoms associated with colorectal cancer are: Change in intestinal habits: constipation, diarrhoea or, more frequently, alternating between the two; Abdominal pain (constant or colicky): pain may be accompanied by a feeling of abdominal distension, nausea and vomiting; Loss of blood from the anus, this can be on its own or mixed in with stools and may be bright red, dark brown or even black in colour (in the latter case, stools may acquire the characteristic “coffee grounds” appearance); Mucous coming from the anus, this can be on its own or mixed with faeces; Weight loss for no apparent reason; Constant tiredness; Nausea or vomiting. There are, however, many other conditions that can cause similar symptoms, so it is important to obtain a medical assessment of the symptoms. It should also be noted that many polyps and cancers of the colon and rectum do not produce symptoms until they become very large. How does colorectal cancer spread? Cancer can spread in two ways: By direct invasion of adjacent structures due to localised growth; By the dissemination of remote cancer cells (metastases) through lymphatic and/or blood circulation. Direct invasion These tumours can grow inside or around the intestines. However, they can also invade the intestinal wall and spread to adjacent structures, such as: Other bowel loops; Abdominal wall; Bladder; Uterus. Metastases Groups of cells can separate from the primary tumour and spread to other parts of the body through blood or lymphatic circulation. These cells can install themselves and grow in other places, such as: Lymph nodes close to the intestine; Liver; Lungs. When a colorectal cancer is surgically removed , the lymph nodes in the vicinity of the tumour are also removed. These lymph nodes will be observed under a microscope to see if they contain tumorous cells. If no tumorous cells are present in the lymph nodes, the likelihood of a cure is greater. How is colorectal cancer treated? Oncological diseases are treated with: Local treatment: surgery and radiotherapy; Systemic treatment (i.e. treatment that affects the whole body): chemotherapy, hormone therapy, antibody therapy, among others. Treatment of colorectal cancer almost always involves surgery . Colorectal cancer surgery is performed by general surgeons. Where necessary, radiotherapy and/or chemotherapy may be used before or after surgery or, in some very rare cases, as an alternative to surgery. In the treatment of colorectal cancer, surgical intervention consists of the dissection of the intestine, with the removal of the region containing the cancer together with the corresponding blood vessels and lymph nodes. In most cases, anastomosis (connection) of the disease-free intestinal extremities is then carried out to restore normal intestinal transit. Most cancers that affect the rectum (the final 15 cm of the large intestine or the first 15 cm from the anus) are also treated surgically . In some cases, large benign polyps and some early cancerous growths can be removed through the anus. However, most rectal cancers are removed via the abdomen . Although as a general rule anastomosis of the dissected intestine is carried out, if the cancer is located very close to the anus it may be necessary to remove not only the whole of the rectum but the anus as well. In this event, it will be necessary to create a permanent colostomy (opening of the intestine through the skin of the abdominal wall). There are some circumstances in which a temporary ostomy (colostomy or ileostomy) may also be necessary. The most common cases in which ostomy is required are: Cancers of the lower rectum (very close to the anus) - with the appropriate surgical technique and use of the latest technology, these can be removed while preserving the anus. However, in most cases, a temporary ileostomy (of approximately 2 months) will be left in place to protect the anastomosis; Where the cancer has caused obstruction or perforation of the intestine, a temporary ostomy may be necessary. However, these days most bowel cancers can be treated without the need for an ostomy. In colorectal cancer, chemotherapy plays a key role in controlling systemic disease and may prolong survival. In the treatment of rectal cancer (affecting the final 15 cm), radiotherapy (most often administered prior to surgery) often plays an important role in local control of the disease, because it reinforces the effect of the surgery. The key to preventing or curing colorectal cancer is in proper screening . This enables: Polyps to be removed when they are discovered; Early detection of cancer. Early detection and timely treatment of bowel cancers results in a high cure rate . What is staging and why is it important? Staging is the inclusion of a cancer into one of several previously defined stages of evolution (stages). Its objective is to predict the likelihood of cure after a cancer has been removed, to help determine which additional treatments will be necessary. Given that, unlike other tumours, the size of a colorectal cancer has little influence on the possibilities of its being cured, the definition of the stages of evolution is based on: Progression of the tumour through the intestinal wall: “is it confined to the wall? has it already crossed the wall?”; Spreading of the tumour to the regional lymph nodes; Spreading of the tumour to other more distant organs or tissues. In accordance with these aspects, tumours are classified as stage I, II, III or IV. Usually, bowel cancer relapses occur in the first 2 years after surgery . Almost all those who relapse (95%), do so within 5 years. The greatest probability of cure, or the best prognosis, is associated with stage I cancers, where more than 90% of patients survive for more than 5 years after surgery. Several tests may have to be done in order to stage the cancer, including: Blood tests for specific compounds; Colonoscopy; Endorectal ultrasound; Chest X-ray; Computerised tomography; Positron emission tomography (PET and PET-CT). The role of differentiation in the treatment of bowel cancers The microscopic appearance of the tumour cells is also important in determining which treatment is to be carried out. This appearance, known as “ differentiation ”, enables tumours to be classified as differentiated, moderately differentiated or poorly differentiated. Patients with well-differentiated tumours have a better prognosis than those with poorly differentiated tumours. This staging and differentiation helps the doctor to decide whether radiotherapy and/or chemotherapy are recommended in addition to surgery. Some statistical data The probability of a person developing a bowel cancer in the course of their life is 6%; in other words, about 1 person in 20 will have the disease . It is estimated that 14% of all cancers diagnosed each year are located in the colon or the rectum. Almost half (40% to 50%) of colorectal cancer patients die as a result of the disease. The frequency of colorectal cancers is increasing and is somehow related to socioeconomic development. The prevalence of the disease is greater in more industrialised countries , such as the USA and Western Europe, and is lower in Africa and South America. In Portugal , the number of annual diagnoses has been growing exponentially, and this disease is responsible for high rates of mortality. It is estimated that 3% to 4% of the population , both male and female, between birth and the age of 70, will be affected by bowel cancer. The peak incidence is in the 6th decade of life (> 50 years). This article was written with the support of physicians and other clinical professionals from the Hospital da Luz network . The content published in the Health Guide is intended for the general public and is provided for informational and educational purposes only. It does not replace individual medical assessment, diagnosis, or personalized clinical advice from a qualified healthcare professional. The content is produced or reviewed by physicians and other healthcare professionals at Hospital da Luz and is based on the knowledge available at the time of publication or the most recent update, as indicated at the beginning of each item.
