Colorectal (Colon) Cancer: Types, Symptoms, Diagnosis, Treatment
Colorectal cancer (also known as colon cancer, bowel cancer, or CRC) corresponds to all tumors located in the large intestine (from the ileocecal valve to the rectum). Worldwide, each year there are approximately one million new cases of colorectal cancer (CRC) and half a million deaths, with a crude global mortality rate of 8.1 / 100,000 inhabitants; those that mainly affect the most developed regions.
There are numerous risk factors related to colorectal cancer, the main ones are: diet, lifestyle, and inheritance. Regarding diet, despite the fact that this has been true for decades, it has not yet been possible to unequivocally determine which foods or nutrients are involved, although there are studies showing an inverse association between the consumption of fiber, vegetables and fruit, and the risk of colorectal cancer, and a direct relationship with the consumption of red meat, smoked foods, and fats. Regarding lifestyle, it is estimated that regular physical exercise reduces the risk of CRC by 40%, while smoking and alcohol consumption increase it.
On the other hand, the effect of hereditary factors on the development of colorectal cancer is well established. Certainly, although in most cases of colorectal cancer are not related to hereditary factors (called sporadic colorectal cancer), in 2-3% of cases, this neoplasm appears in the context of a hereditary disease that includes the syndrome of Lynch or hereditary non-polyposis colorectal cancer (HNPCC), colorectal cancer associated with mutations in the MUTYH gene and familial adenomatous polyposis or other polyposis syndromes.
Regardless of the hereditary or sporadic nature of the CRC, several epidemiological studies have allowed knowing the natural history of this disease. In this sense, it has been possible to establish that the adenomatous polyp is a premalignant lesion that precedes the onset of cancer in most cases so that its removal reduces or even cancels the risk of developing this neoplasm.
Types of Colorectal Cancer
Adenocarcinoma corresponds to 95% of colorectal cancers. Undifferentiated tumors, which are around 20% of colon adenocarcinomas, have less glandular differentiation and have a worse prognosis than well-differentiated tumors. The presence of "signet ring" cells, characterized by the presence of mucin vacuoles that displace the nucleus, is typical of Lynch syndrome, the forms associated with ulcerative colitis and the RCC of young individuals. Squamous cell carcinoma is the most frequent tumor of the anorectal junction (80%), although it is also possible to find carcinomas originating from the transitional epithelium and melanomas. Squamous cell carcinoma is characterized by its local and ganglionic extension, with 30% of the abdominoperineal lymph node involvement, and in 20% inguinal lymph node involvement. Distant metastases occur in 10% of patients.
The prognosis of patients with CRC depends mainly on the depth of transmural involvement and the extent of lymph node involvement. The most frequent routes of dissemination of the CCR are:
Usually follows an ascending anatomical order through the ganglia that accompany the colic vessels. About 40% of the cases present lymph node involvement at the time of diagnosis.
Occurs through the vessels of the colorectal wall and, through portal venous drainage, to the liver, which is the organ most frequently affected by metastasis in colon cancer. Tumors of the lower third of the rectum drain into the inferior cava, which can cause lung, bone, brain metastases, etc., in the absence of liver metastases.
By contiguity can determine invasion and/or fistulization of neighboring organs such as intestinal loops, urinary bladder, vagina, etc.
Peritoneal: rare, but infamous prognosis.
Colorectal Cancer Symptoms
The usual age of presentation of sporadic CRC is between the sixth and eighth decades of life, unlike the hereditary forms in which the diagnosis is usually before 50 years of age The form of presentation depends, to a great extent, on the location of the tumor. Thus, the tumors of the left colon are manifested in general in the form of rectal bleeding and/or changes in the depositional rhythm (constipation or diarrhea). In some cases, the initial manifestation is that of a bowel obstruction. The tumors of the right colon usually cause occult hemorrhage and the symptoms referred by the patient are those attributable to secondary chronic anemia. Tumors in advanced stages can produce nonspecific abdominal pain or the presence of a palpable mass. A rare complication of colon cancer that worsens prognosis is an intestinal perforation, which leads to peritonitis or the formation of an abscess.
Rectal cancer can be manifested by an anorectal syndrome, with rectal urgency, urgency, and diarrhea with mucus and blood. It is not uncommon, in this context, the emission of stools in the form of a tape. When the tumor invades neighborhood organs, the patient may present urinary symptoms attributable to bladder involvement, such as hematuria and pollakiuria, or even pneumaturia, and recurrent urinary tract infections if a rectovesical fistula has been established.
Also, there may be an invasion of the vagina, with the emission of feces through it. In addition to local symptoms, CRC often causes general symptoms, such as asthenia, anorexia, weight loss or fever, and also symptoms that are dependent on the presence of distant metastases.
Colorectal Cancer Diagnosis
CRC should be suspected in any patient with a recent change in depositional rhythm (especially when it occurs at advanced ages, with no apparent cause), rectal bleeding, hematochezia, or chronic anemia attributed to the presence of occult blood in the stool. All these symptoms or signs are common in other clinical entities with which a differential diagnosis must be established. The colonoscopy allows to carry out the exploration of the large intestine and also allows the taking of biopsies to establish histological diagnosis.
Once the diagnosis of CRC has been established, and given that a high percentage of patients have locoregional or distant dissemination, tumor staging should be performed. Complementary tests for the extension diagnosis include a chest CT to rule out lung metastases, and abdominal ultrasound or computed tomography to investigate the existence of liver metastases. Computed tomography is the method of choice to identify mesenteric, lymphatic, and pelvic involvement.
Other explorations such as bone scintigraphy, cystoscopy or gynecological ultrasonography should only be performed when there is suspicion of involvement of a determining organ from the data obtained in the physical examination. At present, the real benefit of positron emission tomography in the staging of the initial lesion is unknown, so its indication is limited to situations in which a neoplastic recurrence is suspected.
In rectal neoplasms it is advisable to perform endoscopic ultrasonography and / or pelvic MRI to determine the degree of infiltration of the intestinal wall and the existence of local adenopathies, especially when considering the performance of neoadjuvant treatment (prior to surgery). Serum levels of carcinoembryonic antigen (CEA) have a reduced sensitivity and specificity for the diagnosis of CRC. However, its determination has prognostic value at the time of diagnosis and its monitoring is useful for monitoring patients after surgical resection.
Colorectal Cancer Treatment
The treatment of choice is surgery. The resection with curative purpose should include the colic segment affected by the neoplasm, with enlargement of about 4-5 cm of healthy intestine at each end, and regional lymph nodes. The type of surgical treatment varies depending on the location of the tumor and the presence or absence of associated complications (perforation, obstruction).
Complementary Treatment of Non-Metastatic CRC
In patients in whom surgical resection has been radical and there is no evidence of dissemination to other organs, it is advisable to perform a complementary treatment in order to reduce the rate of local or distant recurrence and, consequently, improve survival. The complementary treatment includes chemotherapy and / or radiotherapy. In relation to colon cancer, intravenous administration of 5-fluorouracil (5-FU) modulated with folinic acid and associated with oxaliplatin improves both the disease-free interval and survival.
Similarly, in patients with rectal cancer, radiotherapy, either preoperative or postoperative, associated with chemotherapy favors local control of the disease and increases survival.
Treatment of Metastatic CRC
The optimal treatment of CRC with metastatic spread usually requires a multidisciplinary approach and is based on chemotherapy. Several studies show that intravenous administration of 5-FU modulated with folinic acid significantly increases the survival of patients with disseminated disease. In addition, its early administration slows the progression of the disease, prolongs the duration of the asymptomatic period and, consequently, improves the quality of life.
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