Anatomy and function
The stomach is located in the upper abdomen and lies just below the lungs. It is a muscular bag and has three main parts
(i) top portion the cardia which connects with the esophagus,
(ii) the fundus/ corpus, the middle or main body of the stomach and
(iii) the antrum and the pylorus, the last or bottom part of the stomach.
Cardia, fundus, and body/corpus together are called the proximal stomach and the last two parts i.e. antrum and pylorus form the distal stomach.
Few cells in the proximal part of the stomach make acid, a digestive enzyme called pepsin which helps in the digestion of food, and a protein called intrinsic factor that facilitates vitamin B12 absorption by the body.
Movement of food is controlled by two valves (sphincters);one on the upper side where stomach connects with the oesophagus is the cardiac sphincter that controls the movement of food from the esophagus into the stomachand the second sphincter at the lower side of the stomach that connects stomach with the bowel, is called the pyloric sphincter.
Though cancer can start in any part of the stomach, majority of gastric cancers originatein the gland cells (cells that make and release mucus and other fluids) in the inner stomach lining and they are called adenocarcinomas.
Food that is swallowed is pushed down the muscular esophagus into the stomach. The stomach mixes and breaks down the food by releasing gastric juices and digests the food so that our body can absorb it. Then the food moves into small intestine for further digestion. Gastric juices are secreted by the glands in the wall of the stomach. They are acidic in nature.
Stomach continues to produce juices and proteins (enzymes), even when it is empty. To protect the stomach wall from the acid and the pepsin it also produces thick mucus.
It is not known that what causes gastric cancers but research shows that some factors may increase the risk of developing GC.
Having a risk factor does not mean that a person will definitely develop GC. Most of the gastric cancers are related to lifestyle factors.
I) Risk factors that are modifiable
Risk factors includelow consumption of fruits and vegetables, high salt intake, consumption of salty, smoked and poorly preserved foods, cigarette smoking, tobacco chewing and radiation exposure.
Diet is believed to play a major role in the development of gastric cancer. Salt rich, smoked or poorly preserved foods are associated with an increased risk for gastric cancer.
b) Fruit and vegetables
Eating too few fruits and vegetables can increase the risk of getting stomach cancer [4,5] 5,6,]. The United Nations Food and agricultural organization’s (FAO) general recommendation for intake of fruits and vegetables is at least 400 grams per person per day (five serving of 80 g each day)[4,5,6]
Eating foods that are high in salt can increase the risk of gastric cancer [7,]
Most of the salt we eat is in the everyday foods such as pickles, bread, cereals and ready meals. Risk of gastric cancer also increases if you eat lots of pickled vegetables which usually have high salt content [3,8]
There is some research, linking gastric cancer to a diet that is high in processed meat such as ham, bacon, salami and sausages[10,11].
Government of India recommends eating of not more than 90g of red and processed meat a day and advices to reduce it to 70g or less (cooked weight). This is about the same as about 2 sausages[5,9,10]
e) Smoked Food
Smoking of food is a source of release ofcancer causing chemicals. Epidemiological studies indicate frequent intake of smoked foods with the increases rate of cancers in the gastro-intestinal tract [3,11, 12,13, 14,15]
f) Cured Meat:It is a food preservation and flavouring process by the addition of salt, sugar, nitrates and nitrites to foods such as meat, sausages, bacon etc. Both nitrates and nitrites by interacting with H. pylori, can be converted into compounds (nitrosamines) which can increase a person’s risk of developing cancer [3,7, 12,13,14,15]
g) Smoking tobacco:Smokers have about 1.5-2.5 times increased risk of GC than non-smokers [12, 13]
Some Indian studies have correlated smoking with the development of gastric carcinoma particularly for cancers of the upper portion of the stomach near the esophagus[1310,12]. Current smokers were found to be at greater risk than non-smokers and who left smoking habit. Tobacco chewing also increases GC risk. The risk showed an increasing trend with the increase in frequency and amount of tobacco use[12,13,14,15 ]
There is some research linking heavy drinking to the risk of gastric cancer (intestinal type) in men 
i) Helicobacter pylori
It is a bacteria commonly found inside the lining of the stomach and the duodenum. It has been established as the root cause of most of the peptic ulcers and gastritis. After entering the human body H. pylori attacks the mucus lining of the stomach which protects the stomach wall from the acid our body secreted by our body. H. pylori bacteria adapt well to the acidic, low pH environment by secreting an enzyme called urease. Urease neutralizes the acidic environment by converting the chemical urea to ammonia and bicarbonates. These products weaken the mucous lining of the stomach and allow acid to enter to the sensitive coating of the stomach leading to ulcers. Further, the helical shape of H. pylori allows it to burrow into the mucus layer, which is less acidic than the inside space, or lumen, of the stomach. These ulcers may bleed, cause infections, or keep food from moving through digestive tract. Since H. pylori is a slow growing bacterium, most people with H. pylori infection do not show symptoms, but people with the infection are likely to develop peptic ulcers. H. pylori infection can be treated with antibiotics. If neglected, these peptic ulcers and gastritis can lead to gastric cancer and gastric MALT (mucosa-associated lymphoid tissue) lymphoma[17,18,19,20,21]
j) Certain Medical Conditions that cause Gastric Cancer
II. Risk factors that are not modifiable
Age:GC is more common in older people. Majority of GCs develop in people aged above 75 years [ 1].
Gender:Men are nearly twice as likely to get the disease compared to women [1 ].
Certain Genetic Conditions
• Family history of stomach cancer. Risk increases if one had/has a mother, father, sister, or brother who has had gastric cancer [30 ].
• Blood group A:Individuals with blood group A have increased risk for gastriccancer [ 31 ]
• Certain inherited syndromes such as Li – Fraumeni syndrome and Familial adenomatous polyposis (FAP) are associated with familial gastric cancers.[ 32,33]
Toxins:Eating foods contaminated with a fungus called aflatoxin[ 34 ].
Tests and procedures used to diagnose gastric cancer include
• Upper endoscopy (Esophagogastroduodenoscopy or EGD): It is the main diagnostic test used to find stomach cancer. Doctor may recommend this test if someone has certain risk factors or when signs and symptoms suggest gastric cancer presence. Athin, flexible lighted tube containing a micro camera at the end is passed down into your stomach through throat to look for signs of cancer. This lets doctor examine the lining of stomach, if any suspicious area is found; a small piece of tissue is taken from that site (biopsy) for pathology examination. Pathologists confirm presence or absence of tumour by looking the biopsy under a microscope.
• This is a special endoscopy used as part of a special imaging test known as endoscopic ultrasound.
Standard ultrasound uses sound waves to produce images of internal organs such as the stomach. A small wand-shaped probe called a transducer is used with gel a type of conductive medium that enables good contact with the skin and thereby letting the waves transmit directly to the tissues beneath and to the parts that need to be imaged. The transducer gives off sound waves and detects the echoes as they bounce off internal organs. Bounced echoes are processed by a computer to produce a black and white image on a screen.
• In endoscopic ultrasound (EUS), a small transducer is placed on the tip of an endoscope. Sedation is given to the patient then the endoscope is passed down the throat and into the stomach. This lets the transducer rest directly on the wall of the stomach. It lets the doctor look at the layers of the stomach wall, if cancer is there doctor can check the nearby lymph nodes and other structures just outside the stomach to determine the extent of cancer spread. The picture quality is better than a standard ultrasound because of the shorter distance the sound waves have to travel.
• EUS can also be used to help guide a needle into a suspicious area to get a tissue sample (EUS-guided needle biopsy).
• Imaging tests: Computerized tomograpgy (CT) and a Barium swallow test ( a special type of X-ray exam. Imaging is primarily used for staging in gastric cancer and also for post treatment response assessment following Neoadjuvant Chemotherapy (NACT) .
Stage I. At this stage, the cancer is limited to the top layer of tissue that lines the inside of the stomach. Cancer cells may have also spread to a few nearby lymph nodes.
Stage II. Cancer at this stage has spread deeper and into a deeper muscle layer of the stomach wall including spread to more of the lymph nodes.
Stage III. At this stage, the cancer may have grown through all the layers of the stomach and spread to nearby structures and may have spread more extensively to the lymph nodes.
Stage IV. This stage indicates that the cancer has spread to distant areas of the body.
Treatment of gastric cancer depends upon the growth and spread of the cancer. Treatment options for gastric cancer include Endoscopic resection, Subtotal (partial) gastrectomy, and Total gastrectomy, Chemotherapy and Radiotherapy. Palliative surgery is done for unresectable cancer.