Colorectal cancer is a public health problem, considering that in many European countries is first in on the list of malignancies. Although, lung cancer predominates in men and breast cancer in women, adding the two sexes makes colorectal cancer to be the first cause of malignancy in many developed countries. Frequency of colorectal cancer varies by geographic area and is very common in Europe and USA, but less common in South America and Africa. These geographical differences are mainly related to eating habits and to some extent to genetic factors.
The incidence of colorectal cancer is approximately 30-40 per 100.000 inhabitants. Regarding to the ratio between the sexes, colorectal cancer, it is almost equal, with a slight detriment to men. Men / women ratio is about 1.5 / 1. Colorectal cancer is somehow preventable by endoscopic detection of polyps and their removal. Also is well known the role of genetic factors in the development of colorectal cancer (Lynch syndrome).
Colon Cancer Causes
For colorectal cancer are established several factors involved in its production. So there are:
- Dietary factors are involved in the development of colorectal cancer, considering that protective factors are vegetable consumption, dietary fiber, calcium and vitamins. Negative dietary factors are considered to be excess dietary fat and protein, red meat, alcohol, smoking and excessive caloric intake.
- The role of bile acids in colorectal cancer development is debatable, but there are experimental studies that show the involvement of bile acids. Some studies have shown a relationship between cholecystectomy and increased frequency of right colon cancer.
- States predisposing to colorectal cancer are:
- Colorectal polyps is a common condition in gastroenterology practice, so that about 10% of people over 50 years and 30% of people over 70 years have colorectal polyps. These polyps are adenomatous and hyperplastic. Adenomatous polyps ( real polyps ) have several histological types: tubular, tubulo-villous and villous. The highest potential of malignancy have villous polyps and the lowest, tubular polyps lowest. Hyperplastic polyps have no malignant potential. Evolution of malignant colorectal polyps depends on genetic factors, metabolic factors and dietary factors. Malignant polyps have a greater risk if they have a larger size (usually over 2 cm diameter), are more numerous and present more severe dysplasia at biopsy;
- Familial colic polyposis is a pathological situation with a genetic character characterized by the presence of more than 100 colorectal polyps, which occur before 30 years. Genetic transmission is autosomal dominant and the evolution to malignancy is a rule;
- Inflammatory bowel diseases with long evolution, increase the risk of colorectal cancer. This risk is about 10% after 25 years of evolution of ulcerative colitis. The risk of development of colorectal cancer is lower in case of Crohn’s disease;
- Familial predisposition: descendants of a patient with colorectal cancer, have an increased risk of developing the disease, colorectal cancer rate being 2-3 times more common in first degree relatives;
- Lynch syndrome or hereditary non-polypoid colorectal cancer is characterized by the presence of colorectal cancer in many members of the same family, the emergence of disease in young age and association with other malignancies such as ovarian cancer and endometrial cancer. Amsterdam criteria for Lynch syndrome diagnosis are: at least three members of a family diagnosed with colorectal cancer, of which one member to be first-degree relative and at least one diagnosis of colorectal cancer to be put in a patient under the age of 50.
More than half of colorectal cancers are located at the rectosigmoid level. In the ascending colon are located about 20% of cases. Histologically, the majority of colorectal cancers are adenocarcinomas.
Staging of colorectal cancer is made after Dukes classification in the following stages:
- Stage A: tumor located in the mucosa;
- Stage B1: tumor reaches the mucosa muscle;
- Stage B2: tumor invades the entire colon wall, but does not include lymph nodes;
- Stage C: tumor includes lymph nodes;
- Stage D: metastases to distant organs.
Postsurgical survival depends on the stage of the tumor after Dukes classification, being approximately 90% in stage A and 50% in stage C.
Colon Cancer Symptoms
Symptoms of colorectal cancer are suggestive in advanced stages of disease. Most typical signs are:
- Rectorragia is an important sign and appears in colorectal cancers located in the descending colon. Depending on the location of cancer, blood can be red, or clot can be mixed with the stool. In the elderly people, rectorragia always should be considered a sign of malignancy.
- Transit disorders can sometimes suggest a colorectal cancer.
- Partially occlusive syndrome, characterized by intermittent and incomplete stopping of gas transit and fecal transit may raise suspicion of colorectal cancers.
- Anemic syndrome may be a sign of colorectal cancers. It is a iron deficiency anemia which can be mild or moderate.
Colorectal cancer is often asymptomatic in early stages.
Colon Cancer Diagnosis
Diagnosis of colorectal cancer is through these explorations:
- Rectoscopy allows diagnosis of colorectal cancer. With digital rectal examination and anoscopy (which can diagnose the pathology of anal canal), can accurately assess the distal region of the digestive tract.
- Rectosigmoidoscopy allows accurate evaluation of descending colon, where are located 70% -80% of colorectal cancers.
- Colonoscopy is the ideal method for examining the colon, it can view any lesion located in the colon and allows taking biopsies. Allows therapeutic measures, such as polypectomy. It is the only method that can detect vascular lesions of the colon and can perform hemostasis.
- Spiral CT (CT colonography or virtual colonoscopy) allows, using a abdominal CT the virtual reconstruction of the colon and can diagnose colonrectal cancer and colorectal polyps.
- Echo endoscopy (Transrectal ultrasound) allows assessment of extension of colorectal cancer in the colonic mucosal layers.
- Hemocult test, it is used determination of the occult bleeding in the stool. It is a screening test and is aimed at people over 50 years, asymptomatic for diagnose colonrectal cancer. Hemocult II test has a sensitivity greater than Hemocult test and the Immune Hemocult test shows the presence of human hemoglobin in stool.
Colon Cancer Evolution
Evolution of colon cancer depends on the moment of discovery and the time of surgery. If is a Dukes A stage, then survival at 5 years is 90% and in case of Dukes C stage, survival at 5 years is 50%. In the case of colorectal cancer with liver metastases, survival is very low.
Colon Cancer Complications
The most common complications of colorectal cancer are:
- Intestinal obstruction;
Colon Cancer Treatment
The main treatment of colon cancer is surgery. The intervention of colorectal cancer depends on its location. Preoperative evaluation will include assessing of nodal extension and the existence of metastasis in lung, liver and peritoneal.
Postsurgical chemotherapy is indicated for patients in B2 and C Dukes stages. It was observed that postsurgical chemotherapy increases survival time of colorectal cancer patients.
Antiangiogenic therapy, using drugs that inhibit the activity of vascular endothelial growth factor. Clinical studies have shown that the combination of this therapy to chemotherapy, improves survival of metastatic colorectal cancer patients.
Colon Cancer Prevention
Colorectal cancer prevention is a current requirement, given that colorectal cancer ranks first in the world.
Primary prevention consists of measures which encourage people to eat as many vegetables, a diet rich in fiber (whole grain bread, cereal), calcium and reduce consumption of fats, or proteins.
Secondary prevention consist in removing the causes that can lead to colorectal cancer development, especially the discover of polyps and endoscopic resection of them.
Hemocult tests are recommended at one to two years in patients older than 50 years, followed by colonoscopy at people found positive to the test.
After surgical resection of a colorectal cancer, can be done carcino-embryonic antigen to highlight any local recurrences. Tracking ultrasound at 3 months and CT at 6-12 months, is done in the first 3-5 years to detect metastases.