Stomach cancers separated into four distinct types
US researchers have shown that stomach cancer is at least four separate diseases.
The findings, published in the journal Nature, could rapidly lead to new clinical trials focusing on the different forms. Drugs are already available that target the genetic faults behind some of them.
Experts from The Cancer Genome Atlas Research Network – a US-wide government-funded research project – analysed 295 samples of stomach cancers to find similarities that may be targeted when developing treatments.
Research into the biology of stomach cancer and the development of new therapies has been difficult because of the different forms that the disease can take.
Lead author Dr Adam Bass, from the Dana-Farber Cancer Institute, said that, despite stomach cancer being a diverse disease up until now researchers had tended to take a ‘one-size-fits-all’ approach to stomach cancer treatments.
"This traditional approach has likely contributed to the slow progress we have made," he said.
Around 7,000 people in the UK are diagnosed with stomach cancer each year. And there are more than 4,800 deaths from the disease each year.
In the latest study, the researchers ran a number of genetic tests on the samples using six different scanning technologies. The vast amounts of data were then run through computer software to look for patterns, and sort the cancers into separate categories.
There turned out to be four main types of cancer:
- Tumours containing the Epstein-Barr virus (EBV), as well as changes to the PIK3CA gene. This group made up about 10 per cent of the cancers.
- Tumours in which malfunctioning DNA repair mechanisms cause a high rate of genetic changes. About one in five (20 per cent) tumours fell into this subtype.
- The largest category of tumours, making up about half of the cancer specimens, was termed "chromosomally unstable." These cancer cells contained a jumble of extra or missing pieces of genes and chromosomes.
- The fourth group of tumours was termed "genomically stable" as they lacked the molecular features of the other three types. These tumours, making up 20 per cent of the specimens, were largely those of a specific class of gastric cancer called ‘diffuse-type tumours’.
Perhaps surprisingly there was very little sign of a type of bacteria called Helicobacter pylori, a known risk factor for the disease.
This, the researchers speculate, was because of both the advanced stage at which the cancers were diagnosed meant any infection had disappeared, and the way the samples were processed.
Professor Carlos Caldas, Professor of Cancer Medicine at the Cancer Research UK Cambridge Institute, said the research was “very interesting and beautifully constructed.”
“It clearly demonstrates that stomach cancer is four separate diseases, one of which is associated with the Epstein-Barr virus. It also suggests that several drugs already in development for other cancers might be relevant for some of these types of stomach cancer, and this will now need testing in clinical trials.”
In 2012, Caldas led an international team published a landmark Cancer Research UK-funded study, METABRIC, which similarly showed that breast cancer is ten separate diseases.
Large-scale analyses like these, said Caldas, are in many ways the future of cancer research. “They’re simultaneously helping us understand cancer and translate this knowledge into a roadmap to benefit patients”