Overview
Stomach cancer is the fourth most common cancer worldwide with 930,000 cases diagnosed in 2002. However, it is the second most common cause of cancer death worldwide after lung cancer.
There are significant geographical differences in incidence. It represents just 2% of all new cancer cases every year in the United States but it is much more common in Korea, Japan, Great Britain, Iceland and South America. Detailed figures for Europe appear below.
Cancers starting in the lower part of the stomach mainly affect people over the age of 55 and are almost twice as common among men. Cancer in this part of the stomach is less common than it used to be - the incidence has reduced by 50% compared with 30 years ago.
However, cancer arising in the upper part of the stomach near the junction with the oesophagus is becoming more common and can affect people in their 40s.
Most stomach cancers, in both the upper and lower part of the stomach, are adenocarcinomas (cancers that develop from the cells in the glands lining the stomach).
A much less common stomach cancer is GastroIntestinal Stromal Tumour (GIST) or sarcoma of the stomach, which develops in the muscle or connective tissue of the wall of the stomach and other parts of the gut. It makes up 1-3% of all gastrointestinal malignancies.
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Key Figures
| Total number of new cancer cases in Europe (2006) |
3.2 million |
| Total number of cancer deaths in Europe (2006) |
1.7 million |
| Number of new stomach cancer cases (2006) |
159,900 |
|
(96,100 men) |
|
(63,800 women) |
|
81, 600 (EEA) |
|
(50,600 men) |
|
(31,000 women) |
|
80,100 (EU25) |
|
(49,600 men) |
|
(30,500 women) |
| Number of stomach cancer deaths (2006) |
118,200 |
|
(70,400 men) |
|
(47,800 women) |
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Cancer Types
98% of all stomach cancers are adenocarcinomas.
Causes of Stomach Cancer
Infection: Helicobacter pylori (H. pylori) is associated with cancers in the lower part of the stomach (however many people with H. pylori infection do not develop stomach cancer).
Age:
- cancers in the lower part of the stomach usually affect people over 55
- cancers of the upper part of the stomach are becoming more frequent and mainly affect people in their 40s
Diet:
- large amounts of smoked foods, salted fish and meat increase the risk
- fresh fruits and vegetables containing antioxidant vitamins (such as A and C) lower the risk
Smoking increases the risk of developing stomach cancer.
Obesity increases the risk of developing stomach cancer.
Patients with pernicious anaemia (due to failure to absorb vitamin B12) have a slightly increased risk of developing stomach cancer.
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Barrett's Oesophagus
This condition was first described in 1950 as a change in the lining of the lower part of the oesophagus. There is an association between Barrett’s Oesophagus and cancer of the upper part of the stomach. This can progress over time into an adenocarcinoma. Barrett's oesophagus occurs when the stomach contents, including bile and stomach acid, reflux into the oesophagus.
10% of patients with gastro-oesophageal reflux are affected by Barrett's oesophagus and of these 1% per year develop a carcinoma. Overall, Barrett's oesophagus increases the risk of developing cancer by about 30 times.
Barrett's oesophagus does not produce any symptoms in itself and is usually discovered accidentally during other investigations.
Patients with Barrett’s oesophagus are treated with life-long acid suppression. Anti-reflux surgery may be advised in some cases to reduce the chances of progression to cancer.
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Prevention of Stomach Cancer
The big controversy in stomach cancer is whether H. pylori infection should be treated. Given its association with stomach cancer this approach seems logical and may be the reason for the fall in incidence but no randomised controlled trials have proven whether it is effective. In any event, constructing such a trial may be ethically impossible now. Centres vary in their approach but many do treat the infection on the basis that doing so is common sense.
Stopping smoking will reduce the risk over time as will reducing obesity. In addition, it is also beneficial to eat a healthy, well balanced diet that avoids the foodstuffs known to be associated with a higher incidence of stomach cancer.
Patients with Barrett’s oesophagus are often treated with life-long acid suppression. Anti-reflux surgery may be advised in some cases to reduce the chances of progression to cancer.
Creating awareness of the need to take seriously symptoms that might be due to stomach cancer is another important facet of improving outcomes. This is especially the case for the younger group developing cancer in the upper part of the stomach.
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Common Symptoms
Symptoms of stomach cancer tend to be general and vague resulting in late presentation, which impacts on the efficacy of treatment:
- indigestion (particularly if a new symptom)
- heartburn (particularly if a new symptom)
- loss of appetite, especially if combined with feeling bloated after eating
- persistent vomiting
- blood in the stool or black stools (a sign of bleeding into the bowel)
And more generally,
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Diagnostic Tests
Gastroscopy – an endoscopic examination of the stomach and oesophagus. It allows:
- an assessment of the size and character of any tumour that is present
- a biopsy of suspicious areas
Gastroscopic ultrasound - scans the stomach and surrounding structures to see if the cancer has spread to other tissues.
A barium meal is rarely used now as the information it provides is far less useful than an endoscopy.
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Treatment
Surgery is the main form of treatment for stomach cancer but may be supplemented with chemotherapy, radiotherapy or a combination of the two. For GIST, monoclonal antibodies have revolutionised treatment and outcomes.
Surgery
Surgery usually involves a partial or total gastrectomy with lymph node dissection of the nodes near the stomach.
Stomach surgery (particularly removal of the entire stomach) is major surgery and is not suitable for all patients. Some patients may overall benefit more from radiotherapy combined with chemotherapy.
Surgery is also used to treat bleeding from the tumour and obstructions of the pyloric sphincter.
Complications and side effects of surgery
Following partial or total gastrectomy, patients have to eat small amounts of food more often. However, over time, even patients whose entire stomach has been removed can get back to eating near normally. Ensuring these patients have a good diet is very important - patients undergoing further radiotherapy and chemotherapy need at least 1800 calories per day.
Patients who have had their entire stomach removed will not be able to absorb vitamin B12 and so require injections to prevent pernicious anaemia and associated neuropathies.
'Dumping syndrome' is a sudden feeling of weakness, light headedness and sometimes palpitations caused by food being dumped into the small bowel from the stomach. Sugars are absorbed very quickly and this leads to insulin release, which causes the blood sugar to drop quickly. It may happen immediately after eating or some time afterwards. Dumping can be reduced by eating slowly, reducing the amount of simple sugars in the diet (complex carbohydrates take longer to break down and be absorbed) and eating more frequent smaller meals. Advice from a dietician is extremely useful to all patients following surgery for stomach cancer.
Diarrhoea can last for several months after gastrectomy. Anti-diarrhoeal medications can help and some people find that restricting dairy produce is also helpful.
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External Beam Radiation
External beam radiation uses high energy rays generated from machines outside the body to destroy cancer cells. This type of radiation therapy is often used to treat stomach cancer.
External beam radiation usually involves treatments given in small doses several days a week for a few weeks. The treatment itself is entirely painless but there is usually some temporary effect on surrounding tissues.
Radiotherapy combined with chemotherapy (chemoradiation) can be used as the main treatment for stomach cancer. Drugs such as 5 Fluorouracil sensitise the cancer cells to the radiotherapy making it more effective.
This technique can also be used before or after surgery. Recent studies have shown that this form of combined treatment gives better results than surgery alone.
Complications and side effects of radiotherapy
Radiotherapy affects normal cells as well as cancer cells. The effects on normal cells will be reduced as much as possible but nevertheless nearby tissues will be affected and as a result patients experience a range of symptoms including:
- nausea (sometimes with vomiting)
- bowel disturbance
- a reddening of the skin in the treatment area
These symptoms do diminish after treatment has finished and can be treated symptomatically if they occur. Radiotherapy also causes tiredness, which does gradually improve after the treatment has finished.
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Chemotherapy
Chemotherapy may be given as the main treatment for stomach cancer that has spread to other areas of the body and may also be given together with radiotherapy as the main treatment for stomach cancer (see above).
Chemotherapy side effects
Chemotherapy does have side effects which vary according to the drugs used and the individual patient’s response to them. These may include:
- bone marrow suppression leading to anaemia
- susceptibility to infection and bruising
- nausea and vomiting
- hair loss
- diarrhoea
- mouth ulcers
Biological agents – Monoclonal antibodies
Monoclonal antibodies are used in the treatment of many forms of cancer. They target specific proteins necessary to the progression of the cancer, causing very few side effects. In some patients with stomach cancer, proteins on the cancer cells can be targeted by specific monoclonal antibodies slowing cancer cell growth. GIST responds very well to these new agents which generally have very few or just minor side effects.
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Prognosis
Many factors affect prognosis. These include the stage of the stomach cancer, the patient’s age, general health and the individual response to treatment (which will vary). For this reason, statistics can only be considered as a general guide as they are produced by grouping together patients in whom these factors are similar but not identical. These figures are historical, often covering a 10 or 20 year period, and so do not reflect improvements in survival through more modern treatment.
Survival rates indicate the percentage of people who survive the disease for a specific period of time after their diagnosis – usually 5 or 10 years.
Published 5-year survival rates for stomach cancer are
:
- 58% for localised cancers – cancers confined to the stomach
- 29.1% for cancers that have spread outside the stomach but not formed distant metastases
- 3.1% for cancers that have spread outside the stomach and have formed distant metastases
- 12.4% for cancers not staged at the commencement of treatment
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Key Trends
Decreasing numbers of cancers of the lower part of the stomach (which tend to affect people over 55), but increasing numbers of cancers of the upper part of the stomach (which affect a younger group of patients).
Multidisciplinary approaches to the treatment of stomach cancer secure the best quality of care.
The development of treatments tailored to each patient based upon the predicted response of the tumour to available treatments.
Identification of patients with the right receptors to benefit from monoclonal antibodies and other forms of therapy.
The use of functional imaging and PET scanning in the diagnosis of stomach cancer.
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