Causes and risk factors
Diet is believed to be the most important environmental factor. High-fat, low-fiber populations have a high incidence of CRC, while vegetarians and developing populations have a lower incidence. Another important factor is genetic predisposition. Individuals with first-degree relatives (parents, brothers, sisters, children) with CRC and/or adenomas have been shown to have an increased risk of developing this neoplasm. In most cases (70-90%), CRC develops from pre-existing lesions, adenomatous polyps, which, although benign, can develop into a malignant tumor over a very long period of time - about 10-15 years. Since adenomas predispose to the development of cancer, they are called precancerous lesions.
Which are the symptoms?
In its early stages, the disease is asymptomatic or symptoms of irritable bowel syndrome may be present. In the later stages, symptoms depend on the location of the neoplasm: in rectal localization, there is proctorrhagia (loss of bright red blood with feces), false diarrhea (evacuation of abundant mucus) and tenesmus (constant urges to empty); in distal localization of the colon, severe constipation or bowel obstruction; in proximal and rectal localization, mainly anemia. There may be metastases (localization of the disease in places other than the colon due to the spread of tumor cells), mostly to the liver.
How is it diagnosed?
The fecal occult blood test is a very sensitive test that can detect early and asymptomatic neoplasms, and for early diagnosis it should be performed annually after the age of 50. Colonoscopy and double-contrast opaque enema (radiological examination) are the tests that allow diagnosis of the type and location of the neoplasm; even in the case of carcinoma of the rectum, the entire colon must be examined since there may be synchronous tumors (more than one tumor in different locations).
How is it treated?
- Radical surgery: removal of segments of the colon affected by a neoplasm (hemicolectomy) or the rectum, with erasion of satellite lymph nodes, in the absence of metastases.
- Palliative surgery: removal of the tumor mass in the presence of metastases; performed only in cases of severe bleeding or intestinal obstruction and does not change the course of the disease.
- Endoscopic palliation: performed as an alternative to surgical intervention by endoscopic placement of self-expanding endoprostheses or laser treatment, in cases of rectal or sigma obstruction, to avoid intestinal obstruction.
- Chemotherapy: conducted with cycles of drugs, either after surgery to prevent recurrence of the neoplasm and the appearance of metastases (adjuvant chemotherapy), or in preparation for surgery (adjuvant chemotherapy).
- Radiotherapy: very effective in the treatment of rectal neoplasms.
Annual occult blood tests and endoscopy (left colonoscopy or pan-colonoscopy) every five years after the age of 45 are effective in preventing CRC in people with no risk factors. In fact, detection and endoscopic removal of adenomas (i.e., without surgery) interrupts their progression to malignancy, achieving an 80-90% reduction in the expected incidence of colorectal cancer. Colonoscopy should also be performed on all high-risk prisoners, such as those with a personal or family history of colorectal adenomas or colorectal carcinomas.