Stomach cancer – also known as gastric cancer – is the fifth most common cancer worldwide, around 952,000 new cases of stomach cancer were recorded globally in 2012, accounting for seven per cent of all new cases of cancer.

Men are twice as likely as women to develop stomach cancer, and it is more common in older adults; the average age at diagnosis in the United States (US) is 72 years.

Stomach cancer is the third most common cause of death from cancer, as symptoms often only appear at a late stage, which contributes to a poor prognosis.

For example, in Europe and the US the five-year survival rate of stomach cancer is about 25 to 28 per cent, increasing to about 63 per cent if the cancer is diagnosed at an early stage.

However, these survival rates are worse in less developed countries where stomach cancer is typically detected at a more advanced stage.

About 70 per cent of cases of stomach cancer occur in less developed countries with about half of all cases in Eastern Asia, particularly China.

Globally, overall incidence rates of stomach cancer are declining.

This is attributed to a decrease in Helicobacter pylori infection and the use of refrigeration to preserve foods rather than using salt.

Stomach cancer is classified into different types according to location of the tumour: stomach cardia cancer occurs at the top part of the stomach closest to the oesophagus, and stomach non-cardia cancer occurs in all other areas of the stomach.

Stomach non-cardia cancer is more common than stomach cardia cancer, globally, and is most prevalent in Asia.

Rates of stomach non-cardia cancer are declining.

Stomach cardia cancer is more common than non-cardia cancer in more developed countries such as the UK and US, and is increasing in all countries.

In this report from World Cancer Research Federations Continuous Update Project (CUP) – the world’s largest source of scientific research on cancer prevention and survivorship through diet, weight and physical activity – it is possible to analyse global research on how certain lifestyle factors affect the risk of developing stomach cancer.

This includes new studies as well as those included in our 2007 Second Expert Report, Food, Nutrition, Physical Activity and the Prevention of Cancer: a Global Perspective.

In addition to the findings in this report, other established causes of stomach cancer include: Smoking, with an estimated 11 per cent of cases worldwide are attributable to tobacco use, Helicobacter pylori infection causing stomach non-cardia cancer, and industrial chemical exposure, such as wood-processing, food-machine operating, rubber manufacturing, coal mining, metal processing and chromium production being associated with an elevated risk of this cancer.

The global scientific research on diet, weight, physical activity and the risk of stomach cancer was systematically gathered and analysed, and then independently assessed by a panel of leading international scientists in order to draw conclusions about which of these factors increase or decrease the risk of developing the disease.

More research has been conducted in this area since the preceding 2007 Second Expert Report.

In total, this new report analyses 89 studies from around the world, comprising 17.5 million adults and nearly 77,000 cases of stomach cancer.

To ensure consistency, the methodology for the Continuous Update Project remains largely unchanged from that used for the 2007 Second Expert Report.

A summary of the mechanisms underpinning all the findings can be found in the Evidence and Judgements section of the report, but the key findings are as follows.

• There is strong evidence that consuming approximately three or more alcoholic drinks per day increases the risk of stomach cancer.
• There is strong evidence that consuming foods preserved by salting increases the risk of stomach cancer. Research mainly relates to high-salt foods and salt-preserved foods, including pickled vegetables and salted or dried fish, as traditionally prepared in East Asia.
• There is strong evidence that consuming processed meat increases the risk of stomach non-cardia cancer. Processed meat is meat that has been preserved by smoking, curing or salting, or by the addition of preservatives. Examples include ham, bacon, pastrami and salami, as well as hot dogs and some sausages.
• There is strong evidence that being overweight or obese increases the risk of stomach cardia cancer. Being overweight or obese was assessed by body mass index (BMI).
• There is some evidence that suggests consuming grilled or barbecued meat and fish increases the risk of stomach cancer.
• There is some evidence that suggests consuming little or no fruit increases the risk of stomach cancer.
• There is some evidence that suggests consuming citrus fruit decreases the risk of stomach cardia cancer.

Further details can be found in the complete report, available here.

Source: World Cancer Research Federation