Digestive Problems
Diseases: Stomach and Duodenum: Gastric Carcinoma
Thankfully, gastric carcinoma (cancer of the stomach) has become much less common in the USA and other industrialized countries over the last fifty years or so. The reasons for this are not fully understood. Nevertheless this is a serious condition and it remains extremely common in some parts of the world, including China, Japan, and parts of South America. It occurs more commonly in men, especially after the age of fifty years.
What causes cancer of the stomach?
No single cause for stomach cancer has been identified but a number of important risk factors are known. Diets rich insalted or smoked foods have been associated with increased cancer risk in many studies. Similarly, some foods contain nitrites and these chemicals can be converted to more harmful compounds (carcinogens) by bacteria in the stomach. Lack of vitamin C, fruit and vegetables may be important. Stomach cancer is more common in smokers and in those with heavy alcohol intake. In recent years studies have reported that infection with Helicobacter pylori (HP) may increase the risk of gastric cancer three to six fold. This data has come from large population studies comparing the rates of HP infection in patients with gastric cancer compared with patients who do not. It has been estimated that HP infection may actually be responsible for approximately 60% of all cases of stomach cancer but this is controversial. A great deal of research is currently underway to find out more about the role that this bacteria may play in causing gastric cancer. At present, however, the link has not been proven and there is no evidence that offering antibiotic therapy) to healthy people who carry the infection will reduce the risk of developing stomach cancer.
The risk of stomach cancer is also slightly higher in close relatives of patients with the disease but no specific genetic abnormality has been identified and this increased risk in family members may be the result of similar diet and smoking habits etc.
Can gastric cancer be prevented?
In Japan, where gastric cancer is much more common than in the USA, endoscopy screening of healthy people over forty years of age has been able to detect tiny, early tumors before they cause symptoms. Surgery is much more successful when the cancer is at an early stage and improved survival has been reported. In Western countries where stomach cancer is less common screening is unlikely to be effective and would be extremely expensive. If HP infection is proven to be important then it may be possible to prevent stomach cancer by treating the infection.
What are the symptoms and signs of stomach cancer?
In the early stages when the tumor is small there are usually no symptoms. Patients with more advanced tumors usually complain of indigestion and pain in the upper abdomen. Significant weight loss is common, and other symptoms include loss of appetite, nausea and vomiting. Some tumors cause gastrointestinal bleeding or anemia while others cause difficulty swallowing (dysphagia) by blocking the junction between the lower gullet (esophagus) and stomach. Occasionally the condition only presents when the disease is advanced with evidence of spread of tumor to the liver or the abdominal cavity - this may cause a build up of fluid in the abdomen (ascites).
How is cancer of the stomach diagnosed?
Endoscopy is the most important investigation. This should be done promptly in patients with dyspepsia which persists for more than a few weeks or which does not respond to treatment, especially in those over the age of 40-45 years. At endoscopy the inner lining (mucosa) can be carefully inspected and biopsies of any suspicious or abnormal areas can be taken. Sometimes it is not possible to tell whether a gastric ulcer is benign or malignant from the appearances alone and multiple biopsies are usually needed. All patients with a gastric ulcer which is thought to be benign should undergo a repeat examination four to six weeks after treatment to ensure that the ulcer has healed properly.
Once the pathologist has confirmed the diagnosis of cancer further investigations are then carried out to asses whether the tumor has spread through the wall of the stomach to involve adjacent organs and to asses whether or not there is spread of the disease to the liver. This "staging" is necessary to determine whether the tumor can be removed surgically or not. A CT scan is the most important investigation for this and usually gives accurate information but occasionally tiny deposits of tumor have spread (like seeds) thoughout the abdomen and are not visible on the CT scan. For this reason surgeons sometimes wish to perform laparoscopy before deciding whether or not to operate. In this technique the patient is given brief general anesthetic and the surgeon inspects the abdominal cavity carefully with a telescope which is passed through a small incision in the abdominal wall.
What treatments are available for stomach cancer?
Surgery to remove the tumor is the only means of curing stomach cancer. Cure can be achieved in 80% or more of patients with tiny early gastric cancers, but unfortunately, such cases are uncommon outside Japan. For the majority of patients surgery involves removing part of all of the stomach, depending upon the exact location of the tumor.
Surgery may also be necessary in patients who cannot be cured as this may be the only means of relieving distressing symptoms such as blockage of the stomach.
Chemotherapy and radiotherapy treatment given after surgery are not very effective in preventing recurrence of the disease or improving survival. Recently, however, better results have been obtained by giving chemotherapy pre-operatively ("neoadjuvant therapy").
For patients with inoperable tumors, it is sometimes possible to control symptoms (i.e. difficulty swallowing or recurrent bleeding) by laser therapy performed using an endoscope. Similarly, difficulty swallowing or obstruction at the junction between the stomach and duodenum (pylorus) can sometimes be controlled by inserting an expandable metallic tube (stent) through the blocked region to hold it open. Some improvement in symptoms may also be obtained with chemotherapy.
What is the prognosis for stomach cancer?
As mentioned, patients with early tumors (10%) can be cured with surgery. Overall, however, the prognosis is poor with only 10% or patients surviving for five years or more. In cases where the surgeon feels he has succeeded in removing all disease (curative resection), five year survival is around 20%.