The stomach is located on the left side of the upper abdomen. The food that we eat passes through the esophagus (food pipe) to reach the stomach, where acid and some chemicals (enzymes) are produced to assist in the digestion of food. The muscles in the stomach’s wall contract or tighten to mix the food and help the food pass into the first part of the small intestine called the duodenum. 

Cancer occurs due to the uncontrolled growth of cells. These cells travel and spread to other parts of the body. 

Major Types of Stomach Cancer (Gastric Cancer):

• Gastrointestinal stromal tumours: These tumours originate in the interstitial cells located in the walls of the stomach. They are far less common than other tumours.

• Adenocarcinoma: This is the most commonly occurring type of tumour and it originates from a cell that is located on the stomach’s an inside lining called the mucosa. 

• Lymphomas: These tumours originate from the lymphatic tissue situated within the walls of the stomach.

• Gastrointestinal neuroendocrine tumours: These tumours originate from the cells located in the stomach lining which produce hormones. 

Causes of Stomach Cancer

While the exact causes of stomach cancer are not known, studies have revealed that something that alters or damages certain genes in the cell causes the uncontrolled growth of cells.

Nonetheless, there are certain risk factors that are responsible for stomach cancer:

• Diet: In countries, such as Japan, where the consumption of salted and pickled foods is considerably high have reported a high incidence of stomach cancer. The consumption of lots of fruits and green vegetables mitigate the risk of stomach cancer.

• Ageing: The prevalence of stomach cancer is high among older individuals, especially those falling in the age group of 50 years and above.

• Gender: Men are at a higher risk of developing stomach cancer than women.

• Pernicious Anaemia: This condition causes a lack of vitamin B12 and thus, it can increase the risk of stomach cancer.

• Blood Group A: People with blood group A are at a higher risk of stomach cancer.

• Family History: In some instances, gastric cancer has been found to run in the family.

• Long-term infection of the stomach lining with bacterium, which is called helicobacter pylori (H. pylori) increases the risk of stomach cancer.

• Smokers are at a higher risk of stomach cancer.

• If any part of the stomach was removed during a previous procedure due to any condition, the person is at a higher risk of stomach cancer.

Symptoms of Stomach Cancer

During the initial stage, stomach or gastric cancer generally causes no symptoms. While some patients do not experience any symptoms until the later stages of cancer, many others have mild non-specific symptoms that are often ignored for a long period of time. 

• Pain or discomfort in the upper abdomen, generally after eating

• Feeling unwell and being off food

• Indigestion

• Vomiting

• Feeling of fullness after eating

• Loss of appetite and/or weight loss

• The patient may witness blood in their stools (faeces). This generally presents as dark red or black instead of bright red. The dark red colour indicates severe bleeding in the bowel or stomach and it is usually associated with stomach cancer.

• Ascites (build-up of fluid in the abdomen)

• Jaundice (the yellowing of the skin and the eyes)

Note: The people who have the above-mentioned symptoms may not be having cancer. However, they are recommended to consult a doctor and undergo further tests to identify the reason behind these symptoms.

If you experience any symptoms and signs that worry you, consult a doctor/schedule an appointment with a doctor immediately.

Diagnosis of Stomach Cancer

• Health History & Physical Examination: A history of the patient’s health and past diseases and treatments will be taken. The patient will be examined by a doctor for lumps or anything that seems unusual. 

• Blood tests are generally recommended for assessing the overall health or for identifying tumour markers.

• Biopsy: It is performed for confirming the diagnosis. During endoscopy, if the doctor sees anything unusual, then he/she will remove a small sample of tissue from the abnormal area. This procedure is called a biopsy. The sample will be then examined under a microscope so that abnormal cells can be detected and diagnosis can be confirmed. It usually takes a few days to obtain the results of the biopsy. 

• Upper GI Endoscopy: If the doctor suspects stomach cancer, he/she may recommend upper GI endoscopy. An endoscope is a flexible thin telescope that is pushed into the food pipe (esophagus) via the mouth and then directed towards the stomach and the first part of the small intestine also called the duodenum. The endoscope contains fibre-optic channels that allow throw light, which helps doctors look inside the stomach and duodenum. 

Extent and Spread of Stomach Cancer

Thorough investigations are required for determining the extent of cancer in the body. The information collected from these investigations helps doctors determine the stage of the illness, which is necessary for prescribing the correct treatment plan.

The procedures and tests that are used in the staging process are:

• CT scan (CAT scan): This procedure is performed for making a series of detailed images of the areas inside the body, such as the abdomen, pelvis, or chest. The pictures can be taken from multiple angles. The computer that produces these pictures is connected to an X-ray machine. In some cases, a dye is swallowed and/or injected into a vein as it helps the tissues and organs show up clearer. This procedure is also called computerized axial tomography, computerized tomography, or computed tomography. 

• Endoscopic Ultrasound (EUS): A probe is connected at the end of an endoscope to bounce strong sound waves (ultrasound) and high-energy off internal organs and tissues and make echoes. The echoes facilitate the formation of a picture of body tissues known as a sonogram. The procedure is also known as endosonography. 

• MRI (magnetic resonance imaging) with gadolinium: This procedure employs the use of a magnetic field and radio waves for creating a series of detailed images of areas inside the body. A substance called gadolinium is injected into a vein for serving as a contrast just like in a CT scan. The substance collects within the cancer cells and it can be viewed as bright areas during the scan. This procedure is also known as nuclear magnetic resonance imaging (NMRI). One major advantage of MRI is that it doesn’t produce radiation. However, despite this advantage, it is not used widely for detecting stomach cancer.

• Positron emission tomography (PET) scan: A small volume of radioactive glucose is injected into the vein of the patient’s hand. The PET scanner rotates around the patient’s body and clicks pictures of the location where glucose is being utilized in the body. The malignant tumour cells appear brighter in the picture on account of the fact that they absorb more glucose and are more active than normal cells. A CT scan and PET scan may be performed at the same time, which is known as PET-CT. This test provides more information than either of the tests performed alone. 

• Diagnostic Laparoscopy: This surgical procedure is performed for looking at the organs located inside the abdomen for checking for signs of disease. During this procedure, small 1 cm cuts or incisions are made in the abdomen’s wall and a laparoscope, which is a thin, lighted tube, is put into one of these incisions. Other tools may also be inserted through these incisions for inspecting and performing procedures, such as inspecting tissue samples under a microscope for signs of cancer. A solution is then washed over the surface of the organs situated in the stomach and removed for collecting cells, which are then inspected under a microscope for checking signs of cancer. 

How Is Stomach Cancer Treated?

The gastric cancer treatment in India is recommended for each patient depending on the stage and size of the cancer and the patient’s general health.

The patient is advised to discuss the objective of the treatment with their doctor.

For instance:

• The procedure may be aimed at curing cancer. Some gastric cancers can be cured if they are detected and diagnosed in the early stages.

• The treatment may be aimed at controlling cancer. In cases where cure is not realistic, doctors recommend treatment for controlling the growth of cancer and preventing the spread of the disease to other areas of the body. 

• In some cases, treatment is advised to ease the symptoms of cancer. Doctors usually recommend treatments for mitigating symptoms, such as bleeding, obstruction, or pain, for patients with advanced cancer.

Surgery

If the cancer is in the early stages, doctors usually recommend the removal of the tumour as it may be curative. The surgical procedure can be performed either through a robotic/laparoscopic (in certain patient groups) or open approach. The types of procedures used for treating cancer are:

• Total Gastrectomy: It involves the removal of the stomach, parts of the esophagus, lymph nodes, and other tissues located near the tumour. The spleen may also be removed during this procedure. The food pipe (esophagus) is reconnected to the small intestine so that the patient can eat food. 

• Subtotal Gastrectomy: It involves the removal of a specific part of the stomach that contains the cancer cells, lymph nodes, and other organs and tissues located near the tumour if they are affected by the tumour. The spleen may also be removed during the procedure. 

If the stomach is being blocked by the tumour but standard surgery cannot remove cancer, then the following procedures are used:

• Gastrojejunostomy: The part of the stomach located above the cancer is attached to the jejunum (which is a part of the small intestine) to allow the passage of food from the stomach to the small intestine. 

• Endoluminal Laser Therapy: During this procedure, an endoscope (a thin, lighted tube), which is attached to a laser, is put inside the body. A laser refers to an intense beam of light, which is used as a knife for piercing through the obstructing tumour.

• Endoluminal Stent Placement: During this endoscopy procedure, a stent, which is a thin, expandable tube, is inserted in the GI tract to keep the passage open. In cases where the tumour blocks the passage either into or out of the stomach, a procedure is done to put a stent from the esophagus to the stomach or from the stomach to the small intestine so that the patient can eat and swallow normally. 

Endoscopic Mucosal Resection

This procedure involves the use of an endoscope to remove early-stage cancer and precancerous growth from the lining of the digestive tract without requiring surgery.

Chemotherapy

Chemotherapy utilises medicine for controlling the growth of cancer cells, either by stopping them from multiplying or destroying the cells. Chemotherapy drugs can be either injected into a muscle or vein or consumed orally, after which, they enter the bloodstream and reach cancer cells located throughout the body.

In some instances, chemotherapy is utilised in addition to a surgical procedure and this process is called adjuvant chemotherapy. For example, the patient may be given a course of chemotherapy after surgery to kill the cancer cells that may have spread to other parts from the primary tumour and were not detected during routine investigations. Chemotherapy is also needed to be prescribed before surgery in some cases to shrink a big tumour and take proper care of the circulating cancer cells for improving the outcome of the surgery. This process is called neoadjuvant chemotherapy.

Chemoradiation

This therapy combines radiation therapy and chemotherapy to improve the outcome of treatment. When chemoradiation is prescribed after surgery to mitigate the chances of cancer coming back, it is called adjuvant therapy. On the other hand, chemoradiation prescribed before surgery to shrink the tumour is called neoadjuvant therapy. 

Targeted Therapy

This type of therapy uses drugs or other substances for identifying and attacking certain targets on cancer cells. These therapies generally cause less harm to normal cells than radiation therapy or chemotherapy. However, these therapies do cause side effects. Multikinase inhibitors and monoclonal antibodies are the types of targeted therapies used for treating gastric cancer. Presently, they are utilized in the advanced stages of gastric cancer but studies are being conducted for determining if these therapies can be beneficial in the early stages of cancer. 

Radiation Therapy

In this type of therapy, high-energy and strong X-rays or other types of radiation are used for destroying the cancer cells or for preventing their growth. During external radiation therapy, a machine is placed outside the body for delivering radiation to the area/site of the body affected with cancer.