The Hidden Causes of Stomach (Gastric) Cancer

Dr Melvin Look, general surgeon at Mount Elizabeth Hospital, explains what you need to know about gastric cancer and stomach infections.

What is stomach cancer?

Stomach cancer, also known as gastric cancer, occurs when the cells lining the walls of the stomach become cancerous. A mass, or ulcer, may form within the stomach, causing initial symptoms like heartburn, stomach pain, nausea and loss of appetite.

The highest rates of gastric cancer are found in Asia, Eastern Europe and South America. In Singapore, it is the 7th most common cancer in males and the 9th most common cancer in females. And in certain subgroups, the risk is much higher. The lifetime risk for gastric cancer in Chinese men, for example, is about 1 in 50.

Despite advancements in surgery and medical knowledge, most patients in Singapore are still diagnosed with stomach cancer at a late stage, which makes it difficult to treat. Unfortunately, unlike countries like Japan and Korea, Singapore doesn't have any established screening programmes to detect new cases at an early stage.

What are the signs and symptoms of stomach cancer?

In its early stage, stomach cancer usually does not cause any specific symptoms and therefore is not usually detected. When symptoms do occur, they may be vague and are often similar to those caused by other stomach illnesses.

The earliest symptoms of stomach cancer include:

• Indigestion
• Heartburn
• Feeling bloated
• Nausea
• Loss of appetite

However, these symptoms can be caused by several different conditions, so it's important to speak to your doctor for a proper diagnosis.

Advanced symptoms of stomach cancer may include:

• Stomach pain or swelling
• Blood in your stool
• Vomiting
• Weight loss
• Trouble swallowing
• Tiredness

What causes stomach cancer?

The exact cause of stomach cancer is still unknown. What is known is that stomach cancer begins when a cell in the stomach develops changes in its DNA.

As a result, the DNA changes in cells tell the cell to grow quickly and to continue living longer than they are supposed to. The accumulating cells form a tumour that can invade and destroy healthy tissue. Over time, the cells can break off from the tumour and spread (metastasise) to other areas of the body.

Your stomach has 5 parts:

• Cardia: The top part, closest to your food pipe
• Fundus: The upper part, where undigested food is stored
• Body (corpus): The main part, where your food is partially digested
• Antrum: The lower part, where the food mixes with gastric juice
• Pylorus: The bottom part, which acts as a valve to the small intestine

Cancers that originate from the cardia are usually associated with obesity and gastroesophageal reflux diseases (GERD), while those in the antrum and pylorus are usually linked to the helicobacter pylori infection, smoking, a high intake of salty and smoked foods, and a family history of stomach cancer.

Risk factors of stomach cancer

• Type A blood
• Epstein-Barr Virus (EBV)
• Working in coal, metal, timber or rubber industries
• Exposure to asbestos

What's an helicobacter pylori (H. pylori) infection?

8. pylori is a type of bacteria that lives in the stomach. In some cases, it can cause inflamed ulcers to the grow in the lining of the stomach and intestines. This makes it more likely for mutated cells to develop and become cancerous.

No one really knows where the bacteria originally came from or how it was first introduced to humans, but poor hygiene and contaminated food are likely factors in its spread. Almost 60% of adults carry the bacteria, but most of them won't even know it.

If you do have symptoms, they can include:

• Ache or burning stomach pain
• Nausea
• Loss of appetite
• Feeling bloated
• Excessive burping

A course of antibiotics can rid your body of the infection.

What's the Epstein-Barr Virus (EBV)?

EBV is the virus that causes mononucleosis, or 'mono'. It causes flu-like symptoms, including fever, fatigue, rash, sore throat, swollen glands and weak muscles. But again, like H. pylori, you can have it and not even know it. And the virus can stay in your body and become active again, even months or years later.

Unfortunately, there is no specific treatment for mono. The best way to avoid catching it is to stay away from people who have mono symptoms.

While the link between EBV and stomach cancer is relatively new, about 9% of stomach cancers are thought to be associated with it.

Will treating an H. pylori infection reduce my risk of cancer?

Overall population studies do suggest that reducing the number of H. pylori infections can help to reduce the number of cancer cases. In one such study, the incidence of stomach cancer actually decreased by 25%. Therefore, early diagnosis of H. pylori could help to reduce your risk of developing cancer in the future.

If you have any of the symptoms of an H. pylori infection, consult your doctor. They can perform a non-invasive test to rule out other possible causes. A gastroscopy (a small camera inserted down your oesophagus) can also check for any signs or symptoms of stomach cancer at the same time.

How to prevent and reduce your risk of stomach cancer

There are several lifestyle changes you can make to reduce your risk of developing stomach cancer. These include:

• Maintain a healthy weight. If you are overweight or obese, try to aim for a slow and steady pace of losing around 1 kg per week until you reach a healthy weight.
• Eat more fruits and vegetables. Try to incorporate a wide variety of colourful fruits and vegetables in your daily diet.
• Avoid salty and smoked foods. Reduce the amount of salty and smoked foods that you eat. Research shows that those who consumed these foods are more likely to develop stomach cancer than those who don't.
• Stop smoking. Smoking increases your risk of stomach cancer as well as many other types of cancer.
• Screening. If you have an increased risk of stomach cancer due to a strong family history of the condition, your doctor may recommend regular screening, such as endoscopy. Talk to your doctor about this to find out more.