Gastrointestinal (GI) cancer is a cancer that develops from the mucous membrane of the gastrointestinal tract, and can occur in various portions including the stomach, small intestine and large intestine. During the early stages of the disease (when the condition is curable), no symptoms are seen. GI cancer usually arises from the hormone-producing cells present in the mucous membrane of the GI tract. Some of the common substances produced by the GI tumors include serotonin, kallikrein, etc. Usually, the GI cancers grow at a very slow rate and most of the tumors tend to occur around the appendix.
The tumor would most often metastasize if it is larger than 2 centimeters in diameter. There are several risk factors for the development of GI cancers including multiple endocrine neoplasia type I syndrome, atrophic gastritis, pernicious anemia, Zollinger-Ellison syndrome, tobacco smoking, etc. If the cancer spreads to various other parts of the body, a syndrome known as ‘carcinoid syndrome’ develops. If the tumor does not spread to the liver, the hormone-producing cells in the tumor secrete lower amount of hormones that are neutralized by the action of the liver and the blood.
However, if the tumor spreads to the liver, larger quantities of hormones are produced, leading to the development of several symptoms. These include diarrhea, redness of the face and neck, Dyspnea, tachycardia, edema of the hands and the feet, wheezing, cardiac valvular disease, pain and fullness of the abdomen, etc. There are also symptoms of chronic obstruction or intusscuption which may be present (NCI, 2008). Patients suffering from GI cancers can also be affected with strongyloides infection (a parasite). This condition especially occurs in immune-compromised individuals, and can lead to malnutrition (Machado, 2007).
The diagnosis of GI cancers is made based on the history, blood tests, physical examination, urine tests, X-rays, and confirmed with biopsy. The complete blood count includes the counts of the RBC, WBC and the DLC, hemoglobin levels, ESR, etc. The blood chemical analysis includes determination of the various hormones in the blood and chromogranin A assay. A thorough physical examination is conducted to determine various the location and nature of various swellings that may be present. Urine test is done to determine the levels of various breakdown products present in the blood.
Endoscopy helps to study the esophagus, stomach and the small intestine. The physician can take samples of the tumor tissue for biopsy using the endoscope. X-rays and CT scans help to obtained detailed images of the tumor present inside the body. PET scans help the tumor tissues to appear brighter as they have greater metabolism and take up greater amount of glucose. The tumor can spread to various other tissues of the body directly, through the lymph vessels or through the blood. Locally it can spread to the appendix, stomach, intestine or rectum, and through the lymph vessels spread to the nearby lymph nodes.
The outcome of the GI Cancer is good if the tumor is localized and can be resected. In such cases, the 5-year survival rate is about 70 to 90 %. Surgical removal remains the commonest form of treatment for GI cancers. In case of carcinoid symptoms, then removal of the hepatic metastasis is necessary. The outcome of the cancer would be more serious if the tumor is larger in size, non-resectable, involves the lymph nodes or liver, or has recurred after full treatment. Patients with poor prognosis are usually placed on long-term palliative care (NCI, 2008).