Gastric cancer originates from the cells lining the inner mucosal layer of the stomach. As it grows, it spreads through the muscular and serosal layers of the stomach before metastasizing to lymph nodes and distant organs such as the liver, lungs and peritoneal surfaces.
Data from the Singapore Cancer Registry in 2012 shows that gastric cancer is the 7th most common cancer in males (incidence 5.2%) and the 8th most common cancer in females (incidence 3.7%). However, the incidence of gastric cancer is outweighed by its mortality, which is 4th highest in males (6.9% of all cancers) and 5th highest in females (6.2% of all cancers).
Eat healthily to prevent stomach cancer. The high mortality rate is because many patients are often diagnosed in later stages of the disease, when treatment is often more difficult and less successful. Therefore it is essential to have a high index of suspicion in order to improve early detection.
Stomach cancer usually presents in patients between 50 to 70 years of age although younger patients have been to known to be affected as well. It is more common in men with Singapore males estimated to have a lifetime risk of 1:50. Known risk factors for gastric cancer include Helicobacter pylori infection of the stomach and consumption of salted or preserved (cured/smoked/pickled) foods. Smoking and high salt-intake are also associated with a higher incidence of gastric cancer.
The syndrome of hereditary diffuse gastric cancer (HDGC) involves a specific gene mutation which is uncommon. However, other patients with a strong family history of gastric cancer may also be at a slightly higher risk of developing stomach cancer. Certain hereditary syndromes such as familial adenomatous polyposis (FAP), Li-Fraumeni syndrome, hereditary nonpolyposis colorectal cancer (HNPCC) and Peutz-Jeghers syndrome also increase the risk of stomach cancer.
Prevention of gastric cancer usually focuses on reduction of risk factors such as smoking and consumption of preserved foods, and increasing the proportional intake of fresh fruit and vegetables.
Simple tests which raise the suspicion of gastric cancer include blood tests for anaemia and stool for occult blood.
The diagnostic investigation of choice is endoscopy which allows visual identification of suspicious features of the gastric lining mucosa and biopsy for histological confirmation. The typical gastroscopy examination is performed as an outpatient procedure under sedation and local anaesthesia, taking only approximately 10 minutes. Where endoscopy is not available, barium meal X-ray of the stomach is the usual screening investigation for gastric lesions. Investigations to determine the clinical stage of gastric cancer are performed once the histological diagnosis is confirmed & may include X-rays, CT scans, PET scans and endoscopic ultrasound (EUS).
The only curative treatment for gastric cancer is surgery with removal of the stomach and radical excision of all the associated lymph nodes. Patients with early gastric cancer may be suitable for endoscopic resection of the cancer. For early gastric cancer, surgery alone may be sufficient.
The use of adjuvant chemotherapy and radiation therapy is common after surgery for patients with advanced gastric cancer – this reduces the likelihood of tumour recurrence. The chemotherapy options for gastric cancer now include oral-only regimens which are more acceptable to some patients.
In patients who present with large tumours that are locally-advanced which are not suitable for immediate surgery, the option of neo-adjuvant chemoradiation therapy is available in order to prepare them for curative surgery.
For patients with very advanced or metastatic gastric cancer, options for palliative treatment include stenting or surgical bypass of obstructing tumours, radiotherapy for control of bleeding and chemotherapy for reduction of symptoms and tumour growth.
The prognosis of gastric cancer depends on the stage at the time of diagnosis and surgery. The overall stage of the cancer is determined by the degree of spread through the wall of the stomach (T-stage) and the number of lymph nodes involved by the cancer (N-stage) as well as whether or not there are distant metastases (M-stage).
Patients with metastatic disease in Stage 4 usually require palliative care. Patients without metastases who have had complete removal of the stomach cancer and all the associated lymph nodes have a five-year survival of approximately 26% to 95%, provided they follow the recommended adjuvant therapy. As patients with Stage 1 and Stage 2 cancer usually achieve five-year survival exceeding 70%, the importance of early detection of gastric cancer should not be underestimated.