Gastric, or stomach, cancer is one of the major leading causes of death, although the incidence has fallen over the past few years. Usually the cancer is diagnosed in the late stages since most symptoms appear in advanced disease. Almost all gastric cancers are adenocarcinomas, which relate to the site of the cancer, which are the mucus producing cells that line the stomach.
The most common cause for gastric cancer that has been identified is exposure to H.pylori infection which can alter the cells by initially causing inflammation of the normal cells (gastritis) and finally transforming them to cancer cells. Positive correlations attributed to gastric cancer are lack of adequate intake of fruit and vegetables, excessive salt, spices, and smoked foods, smoking, consumption of strong alcoholic beverages, occupational exposure to dust and high temperatures, and a family history of gastric cancer. There are a lot of variations in the incidence of cancer worldwide; in India, even the same geographical region with different ethnic groups can have a different predilection for this cancer.
Initial symptoms for gastric cancer can be confused with other common conditions such as indigestion or gastritis. However, persistent symptoms including heartburn, nausea, vomiting, loss of appetite, loss of weight, bloating, and stomach pain must be investigated. Endoscopy, is used as a procedure where a small camera is inserted into the stomach via the throat and suspicious areas can be seen, and a biopsy (tissue sample) can be taken for evaluation. Other tests include barium swallow by Xray, CT, and PET imaging. Definitive diagnosis is by examining the tissue samples.
Gastric cancer staging includes Stage I, when only the top layer of tissue that lines the inside of the esophagus or stomach is present, with possible involvement of nearby lymph nodes; Stage II, when deeper spread to the muscle layer of the esophagus or stomach wall has occurred with spread to more of the lymph nodes; Stage III, when all the layers of the esophagus or stomach and nearby structures are affected, with extensive nodal spread; and Stage IV, when the cancer has spread beyond the stomach to distant organs and areas of the body.
The goal of surgery is to remove all of the cancer and a margin of healthy tissue, when possible, with removal of nearby lymph nodes. Radiation and chemotherapy can be used before surgery (neoadjuvant radiation/chemotherapy) to shrink a tumor and after surgery (adjuvant radiation/chemotherapy) to kill any cancer cells that might remain in the area around the esophagus or stomach. In cases of advanced cancer, radiation and or chemotherapy are used as an adjuvant to reduce the local recurrences.
When the lymph nodes are involved after surgery the patient needs chemotherapy. If the tumour has involved the full thickness of the wall of stomach or has involved the surrounding structures, radiation to the surgical bed can add to local control and overall survival in such cases. It is preferable to use modulated radiation (IMRT or VAMAT) along with daily image guidance(IGRT) to minimize dose to the surrounding structures like liver, kidneys, heart, lungs and spinal cord..
Another role for radiation therapy in gastric cancer is intraoperative radiotherapy (IORT) that has shown promising results, with increase in 5-year survival rates. This is an alternative method of delivering radiotherapy that allows for a high dose to be given in a single fraction while in the operating room so that other critical structures can be avoided.
Novel methods of treatment drugs used in gastric cancer, called targeted therapies, are those that attack specific abnormalities within cancer cells or direct the immune system to kill cancer cells (immunotherapy), can be used with chemotherapy.