Gastric or stomach cancer is often referred to as an Asian cancer, because it affects Chinese, Japanese and Koreans far more than people of other races.
Associate Professor Jimmy So, head of surgical oncology at the National University Cancer Institute, Singapore (NCIS), said the incidence of this cancer fell dramatically in the West with the advent of the refrigerator.
This is because the cancer is strongly linked to salt and preserved foods. With refrigeration, people in the West ate more freshly cooked food. But preserved foods remain popular in Asia.
Another major cause of gastric cancer is the presence of the Helicobacter pylori bacterium which causes stomach ulcers.
Prof So said not only do many Chinese have H. pylori, but they also have "the more carcinogenic type of H. pylori called Cag-A".
H. pylori is usually transmitted through unclean water or utensils, since it can be passed from one person to another through saliva and other bodily fluids. The United States' National Institutes of Health classifies H. pylori as a "Class 1 carcinogen".
Prof So said although it can be treated with antibiotics, that could lead to resistance, so it is used only if a person is at high risk.
In Singapore, gastric cancer is the seventh most common cancer for men and the ninth for women, affecting more than 500 people a year. In terms of cancer deaths, it ranks fourth.
The good news, however, is that the incidence of this cancer has been falling by about 2.5 per cent a year for several decades, said Prof So, "likely due to improvements in hygiene and the decrease in incidence of H. pylori".
At NCIS, he said, more people are diagnosed earlier, with almost one in two caught at stages one and two now, compared to fewer than one in four about 30 years ago. It is a bit lower on the national level, with one in three caught in the early stages.
But Prof So added that doctors are seeing a "reverse trend" for a particular type of gastric cancer that affects the upper part of the stomach. Called gastric cardia, it now accounts for one in five stomach cancers - up from one in 20 a couple of decades back.
This cancer is largely found in people who are obese and suffer from reflux, where the acid in the stomach rises to the throat. This acid eats into the stomach lining.
Prof So said one in 100 Chinese men would get gastric cancer in their lifetime. It is a little lower for Chinese women, low among Malays and very rare among Indians.
In general, symptoms are non- specific, so Chinese who are over 40 years of age and suffer from gastric pain, vomiting and loss of weight and appetite should check for this cancer, he recommended.
In Japan and South Korea, where the incidence of this cancer is high, there is national screening for people aged 50 and above. As a result, two in three gastric cancers are diagnosed early, before they have spread beyond the stomach.
But national screening is not a feasible option in Singapore because of the high cost and the low risk for other ethnic groups, said Prof So. The incidence of gastric cancer here is also only about a quarter of that in Japan or South Korea. So it is better to find and screen only those at high risk, he said.
The Singapore Gastric Cancer Consortium, comprising doctors and scientists, was formed to develop early detection and better treatment and gain a better understanding of the cancer. It was given a $25 million research grant in 2007 by the National Research Foundation, followed by a second $25 million grant five years later.
The team has come up with some promising tests and treatments. With more knowledge of the cancer, the team has also been able to develop more targeted treatment.
It has identified four risk factors for this cancer, aside from being Chinese, and any Chinese who has all four has 12 times the risk of getting this cancer than the population at large. They are: being 70 years old and older; a smoker; having low stomach acidity; and the Helicobacter pylori bacteria.
The team is finalising a blood test comprising a panel of 24 molecules found in tumours to check for gastric cancer.
Early studies show the test is able to pick out nine in 10 cases of such cancer. But it wrongly identifies one in four cases as cancer.
Prof So said wrongly identifying cancer in someone who does not have it is distressing, but not damaging, as the stomach can be checked with a scope. Of more concern is giving a clean bill of health to someone who does have the cancer.
Having said that, being able to identify nine out of 10 cases is better than any other blood test now on the market.
The group has taken out a patent for this test and, if current trials confirm the level of sensitivity, it will be rolled out for use.
The test is expected to cost about $200 - less than a fifth the cost of a scope.
The most common site of relapse for gastric cancer is in the peritoneum or abdominal cavity. When that happens, "it's bad news", said Prof So, because it is difficult to manage and life expectancy is usually three to six months.
Since 2013, NCIS has been doing a clinical trial where such patients are given intra-peritoneal cavity chemotherapy, which is a bit like dialysis for kidney failure patients, he explained.
Patients have a permanent bottlecap-like metal port inserted in their abdomen. A liquid inserted through the port sloshes around the abdomen, killing cancer cells, then is drained. This is done twice in three weeks, and repeated eight times for the full treatment.
Because the drug is a "big molecule", very little is absorbed into the body. This is carried out in addition to the normal treatment of drugs.
The trial, involving 22 patients, is promising, with 72 per cent surviving one year. The median survival so far is 18 months. Prof So presented the team's findings at a science and medical conference in San Diego in May.
He said: "This is a technically simple outpatient procedure. It has improved the quality of life of patients."
Another new procedure that the group is testing is extensive washing with salt water after surgery to remove the tumour. Surgeons do wash with saline, as a matter of course, to clean up after surgery.
What is different is that instead of washing it just once or twice as is usual, they do it 10 times. The idea is to remove any free cancer cells that might be left in the peritoneum, to reduce the risk of a relapse there.
A total of 16 hospitals here and in Japan, South Korea, Hong Kong and China are involved in this trial that plans to compare washing 10 times, against washing twice or less, in 600 gastric cancer patients. Results are expected by 2021.
Said Prof So: "We will know by 2021 if there are any benefits from this simple, 15-minute technique."
UNDERSTANDING THE CANCER
Professor Patrick Tan of Duke-NUS Medical School and the Genome Institute of Singapore has found two distinct types of gastric cancers that react differently to chemotherapy drugs. Identifying which type a patient has - this can be done once the tumour is removed - means doctors can give him the drug most likely to work.
- To find out more, visit www.singaporecancer society.org.sg or call 6221 -9578.
- Next week: The Straits Times looks at lung cancer.
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