Gastric Cancer (Stomach Cancer)
According to the 2013 statistical report by the Hong Kong Cancer Registry, there are about 1,100 new cases of gastric cancer every year. Men are at a higher risk than women, accounting for about 60% of the total cases. Over 90% of gastric cancers are gastric adenocarcinomas, which are caused by the appearance of abnormal gastric mucosal cells. Other cancers of the stomach include gastrointestinal stromal tumours (GIST) and lymphomas, both of which are relatively rare.
Early symptoms of gastric cancers are very similar to other stomach diseases, and thus can be easily overlooked. Some patients are therefore diagnosed at later stages, when the cancer may have already spread to other organs.
While the causes of gastric cancer are not fully understood, risk factors may include:
- Age: the incidence rate increases with age, especially in people over the age of 50
- History of Helicobacter pylori (H. pylori) infection: increases the risk of gastric cancer by two times
- Long-term pernicious anaemia, gastric ulcers, or chronic atrophic gastritis
- Frequent consumption of foods with high salt content, or smoked, pickled, or canned foods containing nitrosamines
- Family history of stomach cancer
- History of stomach polyps or history of having had part of the stomach removed (stomach surgery or gastrectomy)
Gastric cancer in its early stages may have no obvious symptoms, and even if symptoms do appear, they may be very similar to those of other stomach diseases:
- Bloody or black stool
- Persistent indigestion
- Weight loss and loss of appetite
- Abdominal or even back pain
- Vomiting of blood
Screening and Diagnosis
Examinations for screening and diagnosis of stomach cancer:
- Gastroscopy, also known as upper gastrointestinal endoscopy or oesophagogastroduodenoscopy (OGD)
- Stomach barium meal test
Procedures for assessing tumour metastasis and cancer stage:
- Computed tomography (CT) scan
- Magnetic resonance imaging (MRI)
- Ultrasound scan
- Positron emission tomography (PET)
Treatment of gastric cancer depends on a number of factors such as size, location, and the extent of the tumour, staging of the cancer, and the general condition and age of the patient.
Surgery (D2 Gastrectomy)
Surgery is currently the most effective treatment for gastric cancer. Current surgeries are classified into D1, D2, and D3 gastrectomies, based on the region of the lymph node dissection. D2 dissection is the ideal method as it is suitable for most patients with gastric cancer and simultaneously removes the tumour tissues and nearby lymph nodes.
Due to the complexity of a gastrectomy, the procedure was mainly performed through traditional laparotomy in the past. Nowadays, many gastrectomies are often performed through minimally invasive procedures with robotic technology (i.e. robotic surgery). Both traditional laparotomy and minimally invasive procedures are similar in that they take about three to five hours.
If surgery is unable to remove all cancer cells or tumor tissues completely, chemotherapy and radiation therapy may be arranged for the patient as well, in addition to regular follow-up appointments.
Chemotherapy and Targeted Therapy
Chemotherapy is the use of anticancer drugs to kill cancer cells and inhibit their growth and division. It can be used to relieve symptoms and increase survival rate for advanced disease.
When chemotherapy is used as adjuvant therapy after the surgery to destroy any remaining cancer cells and prevent relapse, it can be administered intravenously (a full course of treatment is about six months) or orally (doses are given over a period of a year) with similar results.
The side effects of chemotherapy drugs vary depending on each drug.
If the growth rate of cancer cells is faster than that of normal cells, angiogenesis (the formation of new blood vessels) often occurs within and around the tumour tissues to supply sufficient nutrients to the tumour. In this case, anti-angiogenesis targeted therapy and chemotherapy will be performed simultaneously to attack the tumour, causing its blood vessels to shrink and controlling its growth.
Radiation therapy is the use of high-energy radiation to destroy cancer cells. New radiation therapy systems such as Tomotherapy, a high-speed helical radiation system, direct radiation energy at the tumour, minimizing exposure of energy to normal cells and reducing the development of possible side effects.
Like chemotherapy, it can be used as adjuvant therapy after surgery to prevent relapse and increase post-surgery survival rate. If the patient is not suitable for surgery, doctors may recommend the use of both chemotherapy and radiation therapy to shrink the obstructive tumour and relieve pain. Radiation therapy is also very useful for palliation in selected sites of distant spread.