Stomach Cancer: Reducing the risks
Stomach cancer affects 1-2% of Australians at some stage in their life. Unless
diagnosed early, it has a very bad reputation, and claims most of its victims
within a few years. In Japan stomach cancer is commoner than in Australia, and
mass-screening with gastroscopy has led to earlier diagnosis and a higher
cure-rate.
The word "stomach" can cause confusion. In general parlance it refers to the
abdomen or belly. The abdomen contains many organs, and, strictly speaking,
the stomach is just one of these. It is an elastic bag, which acts as a food
reservoir, between the oesophagus (gullet) and small intestine. In recent
years, there have been major advances in understanding the cause of most
stomach cancers, and therefore steps can now be taken to dramatically reduce
the risk of ever being affected with this sinister disease.
Stomach cancer is associated with:
-
Helicobacter gastritis
-
reflux oesophagitis
-
pernicious anaemia
Helicobacter gastritis
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Locally advanced stomach cancer
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Helicobacter is the stomach bacterium now known to cause most ulcers of the
stomach and duodenum, and stomach cancers. The incidence of stomach cancer
(otherwise known as gastric carcinoma) has been steadily falling in the western
world, including Australia and New Zealand, since the turn of the century. At
the same time, the incidence of
Helicobacter gastritis
has also been falling. For example, in Australia Helicobacter gastritis is
much commoner amongst people born before World War II, affecting over 30% of
individuals in that age group. It is progressively less common in younger
people. Australians born after World War II harbour the persisting stomach
infection known as Helicobacter gastritis in approx. 5-10% of cases. This
natural decline almost certainly accounts for the parallel decline in stomach
cancer numbers. Perhaps civil engineering is the main factor responsible for
this decline. The exact mechanism of the spread of Helicobacter is still not
well understood. In Japan and some less-developed countries, where
Helicobacter may affect half or more of the population, stomach cancer rates
are still high. The Helicobacter bacterium is usually acquired in childhood or
adolescence, and tends to stay life-long, unless it is eradicated by treatment.
Some cases "burn out" naturally, after many years, but these people are
probably in the highest risk group for developing stomach cancer. Many if not
most people with Helicobacter gastritis have no symptoms at all. Others may
experience vague symptoms, such as abdominal bloating discomfort, occasional
nausea, bad breath or a vague sensation of indigestion. Others may experience
symptoms of a
peptic ulcer
, also caused by Helicobacter in most cases. Burning pain in the upper abdomen
after meals or at night in bed is the typical symptom of an ulcer.
Helicobacter gastritis is easily diagnosed, either by blood test or
gastroscopy. A breath test is particularly useful in testing for a cure, after
a course of Helicobacter eradication therapy. Fortunately, modern therapy
usually eradicates the Helicobacter infection permanently, and over 90% of
patients can be cured with one week of treatment.
Reflux oesophagitis
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Normal oesophago-gastric junction (from a bove)
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There are several types of stomach cancer, and what used to be the commonest
variety attributed to
Helicobacter gastritis
is on the decline. However, an even more aggressive form, in a more
inaccessible site, has increased in incidence in recent decades. This is
cancer at the junction of the stomach and oesophagus, and is now believed to
be a result of long-standing reflux oesophagitis in many cases.
This increase in incidence is confined mainly to males of Anglo-celtic or European ancestry -
women and males of East Asian, South Asian and African descent, irrespective of
the country in which they live, are much less affected. This increase has
been most obvious in wealthier nations, with an ever increasing incidence of
reflux oesophagitis and obesity.
. Reflux oesophagitis may be congenital (this means we are born with it) or
acquired (this means this is a result of our own actions), although in most
cases both factors apply to a greater or lesser degree. As the average
calorie (energy) intake per person rises in so-called developed nations, so does
the incidence of obesity and reflux oesophagitis. This may well explain the alarming increase in cancer of the oesophago-gastric junction,
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Severe reflux oesophagitis
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although it is by no means clear or proven. Somewhat fortunately, many if
not most cases are preceded by a warning sign known as
Barrett's oesophagus
. Barrett's oesophagus is an attempt by the oesophageal lining to protect
itself against repeated acid attacks, as occurs in reflux oesophagitis. [The
most typical symptom of reflux oesophagitis is "heartburn"]. The affected lining
gradually changes to an acid resistant type - clever, isn't it? However, there
is a downside: this new or metaplastic lining, known as Barrett's oesophagus,
has a tendency to develop cancer. This will eventually occur in about 5% of
cases. Biopsies of the Barrett's abnormal lining may be taken
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Barrett's oesophagus (darker area)
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at gastroscopy - these pin-head-sized pieces of tissue are then examined
microscopically, and the likelihood of cancer developing in the foreseeable
future is gauged. In patients with known Barrett's oesophagus, biopsies are
recommended every year or two, and if the abnormal cells start to look
cancerous (dysplasia), the dysplastic cells can be destroyed with a technique known as
Photo-Dynamic Therapy (PDT) or removed with a minimally invasive technique known as Endoscopic Mucosal Resection (EMR). This promising new technique avoids what would
otherwise be very major surgery, involving a dual operation on the abdomen and
chest. It is likely (and common-sense would suggest) that if the reflux is
eradicated, there is less likelihood of Barrett's oesophagus progressing to
cancer. This is as yet unproven. However, patients with Barrett's oesophagus
should be treated with life-long drug therapy to virtually obliterate stomach
acid secretion, or the reflux eradicated with a keyhole (laparoscopic) operation
to repair the faulty lower oesophageal sphnincter (L.O.S.). It is now generally accepted that anti-reflux
surgery should always be approached laparoscopically (ie the keyhole method)
except in occasional cases of re-doing failed older-type anti-reflux
operations, which were performed through a substantial incision in the chest or
abdomen.
Pernicious anaemia
What can anaemia, a disease of the blood, possibly have to do with stomach
cancer? - you may well ask. In fact, pernicious anaemia is caused by failure
of absorption of Vitamin B12 (commonly found in meat, eggs and dairy products),
because of a stomach abnormality. The stomach cells which produce both acid
and a protein necessary for Vitamin B12 absorption, are damaged by an
auto-immune disturbance. This means that the body's immune system mistakingly
destroys some of the body's own cells, in this case the specialised cells of
the stomach lining. Apart from causing anaemia, through lack of a vitamin
essential for healthy blood cell production, the disorder also results in no
stomach acid. This may allow micro-organisms, normally present in food, to
survive passage through what would otherwise be a highly acid stomach. Whether
or not this causes any disease is unknown, but there is undoubtedly an increase
in the risk of stomach cancer in pernicious anaemia patients, which has been
quoted as high as 10% - although experience suggests the risk is not this high. It is not
proven whether regular
gastroscopy
and biopsy to detect pre-cancerous changes is ultimately beneficial, but some
recommend annual screening gastroscopy with biopsies in such cases.
Other rare stomach malignancies
Occasionally, precancerous polyps in the stomach, known as adenomas, may be
detected and removed at gastroscopy, Most stomach cancers are not preceded by
such easily removable polyps. One rare type of stomach malignancy, known as
"MALT-cell lymphoma", closely associated with Helicobacter infection, has been
shown to disappear spontaneously when the Helicobacter infection is eradicated.
If a close relative has had stomach cancer, this does not appear to pose a
much higher risk. The rarer type of gastric carcinoma forming in a
pre-existing gastric adenoma (polyp) may be familial. In the rare situation where many close relatives have been affected,
genetic counselling should be sought.
