Stomach Cancer

Stomach Cancer - What it is

What is stomach cancer?

Stomach cancer is a disease that begins in the stomach, the part of the digestive system which contains, breaks down and digests the food we eat. It is a hollow, muscular organ shaped like a large pouch, located in the upper abdomen, under the ribs. The upper part of the stomach connects to the oesophagus and the lower part leads to the small intestine. Stomach cancer, which is also known as gastric cancer, can affect any part of the stomach.

stomach affected by stomach cancer | SingHealth

How does stomach cancer form and spread?

Stomach cancer forms when cells in the stomach mutate in a way that cause them to grow and divide abnormally causing an ulcer or a mass to form within the stomach. The mass or tumour can eventually spread through the entire wall of the stomach and spread to other parts of the body.

What is the prevalence of stomach cancer?

Stomach cancer is the 8th most common cancer in males in Singapore and the 10th most common cancer among females in Singapore. It more commonly occurs in men and in individuals aged between 50 and 70 years old.

What are the types of stomach cancer?

There are different types of stomach cancer, classified by cell type and where the cancer begins.

Adenocarcinoma: The most common type of stomach cancer, which accounts for 90-95% of stomach cancers, is adenocarcinoma, which starts in the glandular cells of the stomach lining.
Adenocarcinoma may also be classified based on how they look under the microscope – intestinal and diffuse subtypes. Diffuse adenocarcinomas tend to grow and spread more aggressively and are harder to treat.
Gastrointestinal stromal tumours (GIST): GIST is a rare type of soft tissue sarcoma, which forms in the interstitial cells of Cajal (cells in the gastrointestinal tract) and other digestive organs.
Gastric lymphoma: A cancer of the immune system that forms in the stomach wall. They can be mucosa-associated lymphoid tissue (MALT) gastric lymphoma or diffuse large B-cell lymphoma of the stomach. 
Neuroendocrine tumours or carcinoid tumours: Cancer which starts in the neuroendocrine cells, nerve-like and hormone-producing cells, of the stomach.

Stomach Cancer - Symptoms

What are the symptoms of stomach cancer?

There are often no or mild symptoms in the early stages of stomach cancer. As the cancer progresses, symptoms may show and may include:

Persistent indigestion (reflux) or a burning sensation after meals (heartburn)
Upper abdominal discomfort or pain after a meal
Feeling bloated after eating
Feeling very full after a small meal
Loss of appetite
Unexplained and unintentional weight loss
Nausea or vomiting
Blood in the stools or black stools

When stomach cancer is more advanced it may be possible for a healthcare professional to feel a mass in the stomach.

When should you see a doctor?

Make an appointment with your doctor if you have any signs or symptoms that worry you.

Stomach Cancer - How to prevent?

How is stomach cancer prevented?

There are several ways to lower the risk of stomach cancer:

Reduce the consumption of salted and preserved foods
Adopt a diet with high intake of fruits and vegetables. Vitamin A and C, in particular, appear to lower the risk of stomach cancer.
Avoid smoking and inhaling second-hand smoke
Exercise regularly and maintain a healthy weight

Stomach Cancer - Causes and Risk Factors

What causes stomach cancer?

While the exact cause of stomach cancer is unknown, several factors have been found to play a role in its development. These risk factors include:

A chronic infection by a bacteria called Helicobacter Pylori
Gastroesophageal reflux disease
A diet high in salted or preserved (cured/smoked/pickled) food
A diet low in fruits and vegetables
Smoking and alcohol
Family history of stomach cancer
Hereditary syndromes such as familial adenomatous polyposis (FAP), Li-Fraumeni syndrome, Hereditary Nonpolyposis Colorectal Cancer (HNPCC) and Peutz-Jeghers syndrome
Medical conditions that may contribute to stomach cancer such as:

Anaemia (megaloblastic anaemia and pernicious anaemia)
Previous stomach surgeries with partial removal of the stomach (gastrectomy)
A stomach disorder called atrophic gastritis, which results in a lower-than-normal production of digestive juices
Stomach polyps

These risk factors are more commonly seen in people who have stomach cancer. Having one or more of these risk factors does not mean that you will develop stomach cancer. Stomach cancer may still develop in patients with none of the above risk factors.

Screening for stomach cancer

Tests are sometimes used to screen for stomach cancer in people who do not have symptoms. Individuals at higher risk for stomach cancer may be recommended to undergo screening for stomach cancer. They are the same tests used to diagnose stomach cancer (see below).

Stomach Cancer - Diagnosis

How is stomach cancer diagnosed?

Tests and procedures used to diagnose stomach cancer include:

Upper endoscopy or gastroscopy
During the procedure, an endoscope (a thin fibre-optic tube containing a small camera) is passed through the mouth and down the throat to check for abnormal areas in the oesophagus, stomach and duodenum.
Biopsy
If any suspicious areas are discovered during the endoscopy, a tissue sample may be taken and sent to the lab for testing and analysis.
Barium meal X-ray
The patient will be given a liquid containing barium to swallow. This outlines the stomach wall to help locate any tumours or abnormal areas. X-rays of the oesophagus and stomach will then be taken.
Faecal occult blood test
A lab test performed to determine the presence or absence of hidden (occult) blood in the stool.

If stomach cancer is diagnosed, further tests may be required to determine if the cancer has spread and to determine the stage of the cancer. Some of the tests include:

Computerised Tomography (CT) Scan
A CT scan is a type of scan where x-ray beams are rotated around the body to produce a series of x-ray images photographed from different angles. A CT scan is able to show the stomach clearly to confirm the location of the cancer. This test can also be used to look for cancer that has spread to the lymph nodes, liver or abdomen.
Positron Emission Tomography (PET) Scan
Positron Emission Tomography (PET) scan uses radiation to produce 3-D images of the body. Due to the unique characteristics of stomach cancer, PET scan may not be able to detect certain types of stomach cancer.
Exploratory surgery
Exploratory surgery may be recommended to look for signs that the cancer has spread beyond the stomach. This is usually performed laparoscopically (via key-hole surgery), where several small incisions are made, and a special camera is inserted into the abdominal cavity to check for the spread of the cancer.

What are the stages of stomach cancer?

The information obtained from the tests used to diagnose stomach cancer may also be used to stage the cancer. They are:

Stage 0: The tumour is small and only present on the inside surface of the stomach.
Stage 1: The tumour has penetrated into the inner walls of the stomach.
Stage 2-3: Tumours spread deeper into the walls of the stomach with possible spread to nearby lymph nodes.
Stage 4: Tumours have spread through the stomach and to nearby organs. This may also include spread to other parts of the body such as the lymph nodes and to the lining around organs in the abdomen called the peritoneum.

Stomach Cancer - Treatments

How stomach cancer treated?

There are a few effective treatment options for stomach cancer. In general, treatment for stomach cancer depends on the following factors:

Size, location and extent of the tumour
Stage of the disease when the cancer is found
Patient’s general state of health

The main and only curative treatment for stomach cancer is surgery. However, chemotherapy and radiotherapy may also be required for some patients. Endoscopic resection may be possible for very early cancers confined to the mucosa. In advanced stage disease, chemotherapy is generally used in combination with surgery, and radiotherapy may also be administered.

New treatment approaches such as immunotherapy have been shown in clinical trials to be effective for certain types of stomach cancer, either given as single agent or in combination with chemotherapy.

An individual with cancer should be assessed by a specialist to determine which treatment is best suited for them.

Surgery

The type of surgery for stomach cancer varies based on the stage of the cancer.

Upper endoscopy, which is also used to diagnose stomach cancer, can be used to treat early stomach cancer limited in spread to the stomach’s uppermost layers. As a part of this procedure an endoscopic submucosal dissection or endoscopic mucosal resection is performed, and the tumour is resected from the stomach and removed through the mouth.

When the cancer is more advanced, gastrectomy, or removal of the stomach is the recommended surgery.

Partial or subtotal gastrectomy is the removal of a part of the stomach. After a partial gastrectomy, the surgeon will connect the remaining portion of the stomach to the oesophagus or the small intestine, depending on which part of the stomach was removed.
Total gastrectomy is the removal of the entire stomach, suspicious lymph nodes near the stomach and other surrounding tissue. After a total gastrectomy, the surgeon will connect the oesophagus directly to the small intestine.

Partial or total gastrectomy to treat stomach cancer | SingHealth

When stomach cancer has metastasised and spread to the peritoneum, the inner lining of the abdomen, they are known as peritoneal surface malignancies (PSM). In these cases, they may be eligible for a complex and extensive surgery known as cytoreductive surgery (CRS) to remove all visible tumour implants within the abdomen. Following CRS, a high concentration of heated chemotherapy is instilled intra-abdominally to eradicate residual microscopic tumour cells, in a procedure called hyperthermic intraperitoneal chemotherapy (HIPEC).

Chemotherapy

Chemotherapy is sometimes recommended after surgery if there is a risk that the cancer might return. It may also be used before surgery to shrink the cancer, so that it is more likely to be removed completely during surgery.

In patients with advanced stomach cancer, chemotherapy may be used alone or with targeted drug therapy when resection is no longer meaningful or possible.

Radiotherapy

Radiotherapy uses powerful energy beams to kill cancer cells. It can also be used before surgery to shrink the cancer so that it is more easily removed during surgery. In some instances, the doctor may recommend radiotherapy to reduce the risk of a cancer recurrence after surgery, or in the palliative setting to stop bleeding.

Targeted therapy

Targeted drug treatments work by blocking specific weaknesses present within cancer cells, causing the cancer cells to die. Targeted drug therapy is usually combined with chemotherapy for treating advanced or recurrent stomach cancer.

Immunotherapy

Immunotherapy is a drug treatment that helps a patient’s immune system fight cancer. Immunotherapy may be recommended if the stomach cancer is advanced, recurs or spreads to other parts of the body.

Palliative surgery and care

As many advanced cancer patients may not be amenable to cure, palliative surgery or care may be a potential form of treatment. Patients can present with a wide variety of abdominal symptoms owing to tumour related complications such as pain, bleeding, intestinal obstruction, sepsis and jaundice which can substantially decrease their quality of life. Palliative surgery in selected patients has the potential to provide effective relief of symptoms, as can interventions from the supportive and palliative care team to decrease pain and provide comfort.

What are the potential complications of stomach cancer?

If stomach cancer is untreated it can lead to serious symptoms such as gastric outlet obstruction (which can present as intractable vomiting), bleeding from the primary tumour, and accumulation of fluid in the abdomen called ascites, which can lead to increased discomfort from bloating and difficulty to ingest food. Further spread of the disease to liver, lung and bones can also cause organ-specific complications.

If stomach cancer is treated with surgery there are also potential complications, especially if the stomach is removed:

Changes in bowel habits – The body may process food differently, resulting in in more frequent bowel movements or difficulty passing motion.
A feeling of fullness and change in appetite – Post-surgery a feeling of fullness may persist, making it difficult to eat full meals. As your stomach capacity and reserves would have changed, this will take some time and months to adjust to and it will slowly regain some normalcy. Small frequent meals are advised.
Increased bloating or gas – Post surgery, a feeling or bloating or gas may persist.
Vitamin deficiency - Nutrition absorption may be impacted, which may lead to conditions such as anaemia). This should be discussed and addressed by your doctor and necessary deficiencies will be appropriately replaced.
Dumping syndrome – The body may not be able to digest sugar and starch properly, which may cause sudden dips in blood pressure. This should be discussed and addressed by your doctor.

Stomach Cancer - Preparing for surgery

How do you prepare for stomach cancer surgery?

Your surgeon will perform a comprehensive medical work-up including blood tests and scans to see if you are suitable for surgery and advise you on the risks involved. Before surgery, the anaesthesia team will also assess your fitness for surgery and advise you on various aspects of general anaesthesia and pain control after surgery.

Stomach Cancer - Post-surgery care

What can you expect after stomach cancer surgery?

Post-surgery, you will be put on an intravenous infusion (drip through a vein) to replace your body’s fluids until you are ready for fluids, followed by soft, then solid foods.

After recovering from surgery, you will be given regular outpatient appointments to see your team of doctors. During these appointments, you may have blood tests and scans to check if the cancer recurs.

It is important to follow your doctor's advice, keep to your clinic visits and do the recommended scans, so that timely treatment can be administered if the cancer or other problems occur.

Stomach Cancer - Other Information

Can you feel a tumour in your stomach?

In the early stages of the disease, there may not be a palpable mass that can be felt. Only when the mass grows to a significant size, then it can be physically felt. You may start feeling other symptoms of discomfort such as more abdominal bloating, a sensation of fullness or indigestion after taking even small meals before you can actually feel a mass.

Is stomach cancer curable?

Stomach cancer diagnosed in the early stages when it is confined to the stomach as well as regional lymph nodes is curable. Stomach cancer when it has spread to the distant lymph nodes or distant organs such as the lung, liver, peritoneum is no longer curable and treatment given is palliative with aims to control or shrink the tumour, but is unable to eradicate all disease.

What is the prognosis (outlook) for people who have stomach cancer?

There are many factors that influence the prognosis of patients with stomach cancer, such as the location, type and stage of the cancer, as well as the patient's age and overall health. Stomach cancer is usually most treatable when it is found early, before the cancer has spread to other parts of the body.

Is stomach cancer an aggressive cancer?

Yes, stomach cancer can be aggressive, especially in its advanced stages. However, the outlook can vary depending on the stage at which it is diagnosed and other factors.

What is the biggest symptom of stomach cancer?

There is no one biggest symptom of stomach cancer, and it can present any of the following symptoms:

Early satiety – sensation of increasing abdominal bloating or fullness even after a small meal
Loss of appetite and loss of weight
Anaemia, bleeding in the stools from the primary tumour
Persistent indigestion or reflux
Nausea or vomiting after a meal

How long can stomach cancer go undetected?

Stomach cancer can be difficult to detect in its early stages because it often produces no symptoms. As the cancer progresses, the symptoms that appear such as persistent indigestion or upper abdominal discomfort or bloating can be mistaken for normal gastrointestinal issues. Stomach cancer can go undetected for some time before the symptoms become concerning enough for the patient to go for diagnostic testing.

For more information, click here for the English publication on Stomach Cancer.
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For further enquiries on Stomach Cancer, please call the Cancer Helpline at (65) 6225 5655 or email to [email protected]