Stomach cancer, also known as gastric cancer, begins when cells in the stomach lining grow abnormally and form a tumour. Over time, these cancerous cells can invade deeper layers of the stomach wall and spread to nearby lymph nodes, organs, or even distant parts of the body. Most stomach cancers develop slowly over several years, often starting with precancerous changes in the inner lining that go unnoticed.
Stomach cancer starts when abnormal cells grow in the stomach lining and form a tumour, often without early symptoms.
A significant proportion, approximately 58% of cases, are identified at Stage III or IV, contributing to lower survival outcomes.
Stomach cancer is categorised into stages based on how far the tumour has grown and whether it has spread to lymph nodes or other parts of the body.
Stage 0 involves abnormal cells confined to the innermost lining of the stomach (mucosa).
Stage I indicates early invasion into the mucosa or submucosa and possibly limited spread to one or two nearby lymph nodes.
Stage II means the tumour has reached the muscular layer of the stomach wall or involves more lymph nodes.
Stage III shows deeper invasion into the outer stomach layers and/or extensive involvement of regional lymph nodes.
Stage IV is advanced cancer that has spread beyond the stomach to distant organs such as the liver, lungs, or abdominal lining.
The stage at which stomach cancer is diagnosed plays a critical role in determining the treatment plan and chances of long-term recovery.
Stomach cancer may progress from the inner lining (mucosa) in Stage 0 to deeper layers like the submucosa and muscular layer, and eventually spread to distant organs by Stage 4.
What are the different types of stomach cancer?
There are several types of stomach cancer, classified based on where they originate in the stomach and the kind of cells involved. The main types include:
Adenocarcinoma – this is the most common form, accounting for over 90% of stomach cancers. It develops from the glandular cells lining the stomach’s inner surface. Adenocarcinoma can be further categorised into:
Intestinal type – often linked to environmental factors like diet or H. pylori infection, and tends to grow more slowly.
Diffuse type – tends to spread more aggressively and is not strongly linked to environmental causes.
Gastrointestinal stromal tumour (GIST) – a rare cancer that arises from specialised nerve-related cells in the digestive tract wall, most commonly in the stomach and small intestine, which help regulate the movement of food through the gut.
Lymphoma – cancers that originate in the immune system tissue found in the stomach wall. Although uncommon, gastric lymphomas can behave quite differently from adenocarcinomas and often respond well to non-surgical treatments.
Hereditary diffuse gastric cancer (HDGC) – a rare inherited condition caused by mutations in the CDH1 gene. Individuals with this condition have a high lifetime risk of developing diffuse-type gastric cancer and are often advised to consider preventive measures.
What causes stomach cancer?
Stomach cancer typically develops slowly over time, beginning with damage to the stomach’s inner lining. This damage can come from infections, chemical exposure, genetic mutations, or anatomical changes that disrupt normal stomach function. These factors contribute to cellular changes that may eventually become cancerous.
Chronic Helicobacter pylori (H. pylori) infection — this is one of the most well-established causes of stomach cancer. The bacteria can persist in the stomach lining for years, triggering ongoing inflammation. Over time, this chronic irritation may lead to progressive changes in the cells, moving from inflammation to atrophy, metaplasia, dysplasia, and eventually malignant transformation. If you are concerned about H. pylori infection, Dr Tan can guide you on appropriate testing and recommend effective treatment to help eliminate the bacteria and lower your cancer risk.
Carcinogenic compounds from preserved foods — nitrates and nitrites found in smoked, salted, or preserved foods can be converted by stomach bacteria into harmful compounds called N-nitroso compounds. These chemicals directly damage the DNA of stomach lining cells and contribute to cancer development.
Inherited genetic mutations — in certain families, mutations passed down through generations can cause stomach cancer to develop even without other risk factors. The most notable is the CDH1 gene mutation, which leads to Hereditary Diffuse Gastric Cancer (HDGC). This mutation affects how cells stick together, allowing cancer to spread more aggressively.
Structural or functional changes in the stomach — conditions such as chronic bile reflux, autoimmune gastritis, or previous partial gastrectomy can alter the stomach’s normal environment. These changes weaken the stomach lining’s defences and create conditions where abnormal cells can emerge and grow uncontrollably.
Each of these causes contributes to long-term damage or disruption in the stomach lining, setting the stage for cancer to develop over time.
What are the symptoms of stomach cancer?
Stomach cancer can be difficult to detect early because symptoms are often mild, non-specific, or mistaken for common digestive issues. As the cancer grows, the symptoms become more persistent and may signal more advanced disease.
Early symptoms — These are often subtle and may come and go
Persistent indigestion or heartburn
Feeling full quickly after starting to eat (early satiety)
Mild upper abdominal discomfort or bloating
Loss of appetite
Later-stage symptoms — These tend to be more obvious and concerning
Unexplained weight loss
Persistent nausea or vomiting
Difficulty swallowing (especially for tumours near the top of the stomach)
Vomiting blood or passing black, tarry stools (a sign of internal bleeding)
Constant fatigue or weakness
Abdominal pain that doesn’t go away
Stomach cancer symptoms often mimic those of less serious conditions, which is why many cases are diagnosed at a later stage. If any of these symptoms persist or worsen over time, it is important to seek medical advice for proper evaluation.
Persistent abdominal pain is one of the warning signs that may indicate the presence of stomach cancer.
Who is at risk of stomach cancer in Singapore?
In Singapore, those more likely to develop stomach cancer include:
Men over 50 years of age — incidence rises with age and is significantly more common in males, particularly after age 50.
Individuals with family histories or inherited cancer syndromes — although hereditary cases are rare (approximately 1–3%), those from families with stomach cancer, or known gene mutations (e.g., CDH1 in Hereditary Diffuse Gastric Cancer), are at increased risk .
Additional risk factors — these include chronic stomach conditions like atrophic gastritis or bile reflux, and prior stomach surgeries, as these alter the stomach lining and may contribute to cancer development.
How is stomach cancer diagnosed?
Diagnosing stomach cancer typically begins with a thorough medical evaluation based on symptoms such as persistent indigestion, unexplained weight loss, or vomiting. If cancer is suspected, the following diagnostic procedures are commonly used:
Gastroscopy (upper endoscopy) — this is the most definitive test for detecting stomach cancer. A thin, flexible tube with a camera is passed through the mouth into the stomach for a direct visual inspection of the stomach lining. Suspicious areas can be biopsied during the procedure.
Biopsy — during gastroscopy, small tissue samples are taken from abnormal areas. These are examined under a microscope to confirm whether cancer cells are present and, if so, what type of stomach cancer it is.
Imaging tests — after diagnosis, imaging helps assess how far the cancer has spread:
CT scan of the chest, abdomen, and pelvis evaluates tumour size and involvement of nearby organs or lymph nodes.
Endoscopic ultrasound (EUS) may be used to assess the depth of tumour invasion and nearby lymph nodes.
PET-CT scan may be recommended to detect distant spread (metastasis).
Staging investigations — additional tests like diagnostic laparoscopy (a minimally invasive surgical procedure) may be done to check for small tumours or spread that imaging might miss, especially before surgery.
Accurate diagnosis and staging are crucial in planning the most appropriate treatment and predicting outcomes for stomach cancer patients.
What are the treatment options for stomach cancer in Singapore?
In Singapore, treatment for stomach (gastric) cancer typically involves a multidisciplinary team including surgeons, medical and radiation oncologists. The primary options available are surgery, chemotherapy, radiotherapy, targeted therapy, and immunotherapy. Treatment plans often combine these modalities based on tumour stage, location, and individual health.
Surgery — The primary curative treatment
Surgery remains the only potentially curative option. Early-stage tumours may be removed using minimally invasive techniques such as endoscopic mucosal resection (EMR) or endoscopic submucosal dissection (ESD). For more advanced localised cancers, partial (subtotal) or total gastrectomy is performed, often accompanied by lymph node removal.
Chemotherapy — Before and after surgery, and for advanced disease
Chemotherapy uses combinations of drugs like cisplatin, 5‑FU (fluorouracil), capecitabine, oxaliplatin, docetaxel, irinotecan, and epirubicin. It is used:
Neoadjuvantly to shrink tumours before surgery
Adjuvantly to reduce recurrence risk post-surgery
Palliatively for non-surgical patients or metastatic disease
Radiotherapy — Complementary treatment
Radiotherapy may be used:
Adjuvantly, often combined with chemotherapy after surgery to eradicate residual disease
Neoadjuvantly, to reduce tumour size pre-surgery
Palliation, to relieve pain or bleeding in advanced cases
Modern techniques such as 3D‑CRT and IMRT are commonly used.
Targeted therapy — Precision based on tumour markers
For tumours overexpressing HER2 (about 13–22% of cases), trastuzumab (Herceptin) combined with chemotherapy is used for advanced disease. Ramucirumab, an anti-angiogenesis agent, is also used, often alongside paclitaxel, as second-line therapy for metastatic disease.
Immunotherapy — Harnessing the immune system
Checkpoint inhibitors such as pembrolizumab and nivolumab (targeting PD‑1) are employed for certain advanced or metastatic gastric cancers to boost the immune response against tumours.
Summary
Stomach cancer, or gastric cancer, is a serious condition that often develops slowly over time due to chronic irritation or damage to the stomach lining. In Singapore, it remains one of the top ten most common cancers, with a significant number of cases diagnosed at a late stage. Most stomach cancers are adenocarcinomas, but other types such as gastrointestinal stromal tumours (GIST), lymphomas, and hereditary forms also exist.
The disease can be caused by long-standing H. pylori infection, exposure to carcinogenic compounds in preserved foods, inherited genetic mutations, and structural changes in the stomach. Symptoms are often vague in the early stages, such as indigestion, early satiety, or bloating, and become more severe as the cancer progresses, including weight loss, vomiting, and bleeding.
Diagnosis typically involves gastroscopy and biopsy, followed by imaging tests to determine the extent of the disease. Treatment in Singapore is highly individualised and may include surgery, chemotherapy, radiotherapy, targeted therapies, and immunotherapy depending on the stage and tumour characteristics.
If you are experiencing persistent digestive symptoms or have concerns about your stomach health, schedule a consultation with Tan Siong San Surgery for a thorough evaluation and personalised care.
Frequently Asked Questions (FAQs)
Early symptoms of stomach cancer can include persistent indigestion, bloating, early fullness, or vague upper abdominal discomfort. These symptoms are often overlooked or mistaken for common digestive issues.
Survival varies depending on the stage at diagnosis. Early-stage stomach cancer has a better prognosis, while advanced stages may be managed with treatment to prolong life and improve comfort.
Stage 4 stomach cancer is serious, but not always immediately fatal. Some patients respond well to targeted therapies or immunotherapy and may live for several months or even years.
Yes, stomach cancer can be cured if detected early and treated appropriately with surgery and/or other therapies. Late-stage cancers are harder to cure but may still be managed effectively.
Stomach cancer can develop silently for years before symptoms appear. That’s why it’s often diagnosed at a later stage when symptoms become more noticeable.
Stomach cancer usually affects people over the age of 50, and is more common in men. Risk increases with age and certain genetic or environmental factors.
Yes, stomach cancer may be inherited. Individuals with a strong family history or certain gene mutations (like CDH1) are at increased risk and may benefit from genetic counselling.
Some stomach polyps or lesions may become cancerous over time. Regular monitoring or removal is recommended if there’s a risk of malignant transformation.
Not always. Depending on the tumour’s size and location, some patients undergo partial gastrectomy, while others may need total removal. Your doctor will advise based on staging.
Recurrence depends on the cancer’s stage, treatment type, and follow-up care. Regular surveillance with scans or endoscopy helps detect any return early.
Options include second-line chemotherapy, targeted therapies (like ramucirumab), and immunotherapy (like nivolumab or pembrolizumab), depending on the cancer’s characteristics.
Most patients stay in the hospital for about 1 to 2 weeks after major surgery, with full recovery taking a few months depending on the extent of surgery and individual health.
This article has been medically reviewed by Dr. Tan Siong San
Dr Tan is a Senior Consultant Surgeon with over 25 years of clinical experience in the field of Hepato-Pancreato-Biliary (HPB) surgery treating conditions affecting gallbladder, liver and pancreas.
