The Stomach – An Overview
The stomach is a hollow organ forming a part of the digestive tract located in the upper part of the abdomen. Swallowed food passes down the food pipe into the stomach where it is further digested. The digestive secretions of the stomach include acid (hydrochloric acid) and enzymes (chemicals) that act upon the food to aid in digestion. The food is thoroughly mixed with the digestive secretions by mixing movements of the stomach muscles. This partially digested food is propelled into the duodenum (the first part of the small intestine) for further digestion and absorption.

Cancer arising in the stomach is termed gastric cancer.

Risk factors of Stomach Cancer
The exact cause of stomach cancer is not known but there are certain risk factors associated with an increased risk of development of stomach cancer.

• Being overweight (BMI 25-30) or obese (BMI > 30)
• Smoking
• Diet deficient in fresh fruits and vegetables
• Ingestion of salty food eg pickles and smoked food – in countries such as Japan
• Diet high in processed meat such as bacon, ham , salami and sausages
• Chronic Helicobacter pylori (H pylori) infection
• Alcohol consumption
• Decreased immunity
• Male sex
• Increasing age – Persons over the age of 60 years
• Low stomach acid secretion (hypochlorhydria)
• Occupational exposure to certain chemicals eg asbestos, inorganic lead compounds
• Family history of stomach cancer
• Inherited gene for stomach cancer eg E-Cadherin (CDH1) gene.
• Persons with Blood group A
• Previous radiotherapy for other cancers such as breast cancer, testicular cancer, head and neck cancer and cancer cervix

Symptoms of Stomach Cancer
Stomach cancer may not become symptomatic until later in the disease. The common symptoms include the following

• Pain and discomfort over the upper tummy (abdomen), particularly after food
• Bloating and indigestion symptoms after eating
• Weight loss and/or loss of appetite
• Nausea and vomiting due to growth blocking passage of food from the stomach
• Passing black stools (due to blood from the growth which becomes black on mixing with the stomach acid)
• Tiredness and breathlessness (due to anemia caused by loss of too much blood from the growth)

Histological types of stomach cancer
• Adenocarcinoma (cancer arising from the lining of the gastric glands) (most common type)
• Lymphoma stomach arising from lymphatic tissue within the stomach
• Sarcoma – Arise from muscle or connective tissue in the stomach
• Carcinoid tumors – Arise from cells in the stomach that secrete hormones

Diagnosis of Stomach Cancer
When the patient sees his family physician or GP for symptoms such as weight loss, loss of appetite or undue tiredness, the GP will take a detailed history and perform a thorough physical examination. If he suspects the presence of an abnormality in the stomach, the patient will be referred to a gastroenterologist for further evaluation and management.

Blood tests:
Full blood count, liver function tests, kidney function tests will be done to assess the status of the patient.

Upper GI (gastrointestinal) Endoscopy
The gastroenterologist will perform an upper GI endoscopy which involves passage of a thin flexible lighted tube (endoscope) with a small video camera at one end, down the throat. The tube allows visualization of the interior of the stomach and duodenum to identify abnormal looking areas.

Cancer stomach may appear as an area of depression with a bleeding surface (ulcer), an exophytic protruding growth, or diffuse thickening of the stomach lining (linitis plastica).

Biopsies from the abnormal areas can be obtained by passing specialized instruments through the endoscope and obtaining samples of these areas and sending to the pathology lab for analysis.

Endoscopic Ultrasound (EUS)
This test combines endoscopy with imaging of the stomach ultrasound. This test may be done under anesthesia.

During the test, the ultrasound probe is placed on the tip of an endoscope. While the patient is asleep, the endoscope is passed down the throat and into the stomach. This allows the probe to rest directly on the interior of the stomach close to the abnormal area.

The layers of the stomach wall and adjacent lymph nodes and other structures just outside the stomach are seen. The picture quality in EUS is better than a standard ultrasound because of proximity of the tissue to the probe. A biopsy of the abnormal area can be obtained during EUS.

Imaging Tests
Imaging tests such as plain x-ray abdomen with contrast (barium meal study). The barium contrast will coat the lining of the stomach and small intestine and delineate the presence of any mass.

CT (computerised tomography) scans and MRI (magnetic resonance imaging) scans outline clearly abnormalities of the stomach and adjacent soft tissues.

PET (positron emission tomography) scans to determine if a suspicious looking area may be cancer,
to determine the size of growth and the extent of spread and to look at several parts of the body for possible spread (metastases) simultaneously.

Staging of Stomach Cancer
Once the diagnosis of cancer is confirmed further tests may be done to assess the extent of the growth and presence of spread to lymph nodes and distant organs such as the lungs and the liver.
Staging of the cancer is done by the treating physician to determine the type of treatment. The most commonly used staging system is the TNM (tumor node metastases) system.

Treatment of Gastric Cancer
Gastric cancer treatment depends on the size of tumor, tumor stage and the patient’s general condition.

Early Gastric Cancer – Stage 0/1
Early gastric cancer refers to growth that is limited to the inner layers of the stomach irrespective of spread to nearby lymph nodes.

These cases are treated with endoscopic (minimally invasive) or open surgical removal of the tumor (subtotal gastrectomy) and removal of local lymph nodes followed by adjuvant therapy including H pylori eradication treatments and radiotherapy as necessary.

Gastric Cancer – Stage 2/3
Tumor involves outer layers of stomach and/or adjacent nodes but no distant spread.
Surgical resection of the tumor may be combined with systemic chemotherapy either before surgery (neoadjuvant chemotherapy) or after surgery to kill tumor cells. Chemotherapy may be combined with radiotherapy as well in certain cases.

Advanced Stage 4 stomach cancer with distant metastases
Palliative (non-curative) surgery to relieve pain and obstructive symptoms plus chemoradiation if patient is able to tolerate these when the primary tumor is inoperable.
A feeding tube or parenteral nutrition may be necessary in advanced gastric cancer patients.

Other options include targeted therapy depending on the presence of certain proteins in the cancer cells as detected by specialized tests (immunohistochemistry). Treatments include Trastuzumab (in Her2 positive cancers) or Ramucirumab (in vegf positive cases).

Immunotherapy to stimulate the immune system to act against the tumor cells with pembrolizumab (Keytruda) may be an option in some cases.