Learning from cancer map of the world

We think of cancer as one disease. In fact it is more than 100 different diseases, affecting all parts of the body with different causes and outcomes. The incidence varies widely across the world, influenced by diet, smoking and drinking, infection, climate and social factors. So what is this global pattern, and what light does it throw on the development of cancer?

Breast cancer

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This is the commonest cancer in women in the developed world. Every year more than 44,000 women are diagnosed with this disease in the UK, more than 100 a day, and rates here have increased by 50 per cent over 20 years. Worldwide more than one million cases are diagnosed every year. The rise is thought to be driven by changing patterns of child rearing. Women are delaying childbirth, having smaller families and spend less time breast feeding, all of which behaviours increase the risks. But while cases are rising, the death rate is falling – by a third in the UK in the past 20 years – thanks to better treatments.

Bladder cancer

The highest incidence in the world is in Egypt, where it is the most common cancer. The cause is endemic schistosomiasis (bilharzia), caused by a parasite. In the UK, bladder cancer is the fifth most common, with 10,000 new cases a year. It is more than twice as common in men as women. The causes are smoking and exposure to industrial chemicals. It can take 20 to 25 years to develop. Rates peaked in the UK in the 1990s and have since fallen by a third. Chemicals implicated in its genesis were banned decades ago and smoking has fallen.

Cervical cancer

This is a disease of poverty. It is one of the few cancers caused by a virus – the human papilloma virus (HPV) – which is transmitted through sex. It is commonest in Central and South America, Sub-Saharan Africa, and India and the Far East. In the UK, around 2,700 women are diagnosed each year and there are more than 1,000 deaths. From last month, an HPV vaccine has been offered to schoolgirls in the UK which is expected to prevent 70 per cent of cases of the cancer.

Bowel cancer

It is the fourth most common cancer worldwide, though it tops the table in only one country, the United Arab Emirates. In the UK, it is the third most common cancer (after breast and prostate), with more than 36,000 cases diagnosed a year and 16,000 deaths. The cancer is linked with a Western diet high in red meat and short on fruit and vegetables, and a sedentary lifestyle. The lowest incidence is in developing countries of Africa and Asia where diets are largely vegetarian.

Kaposi's sarcoma

This rare cancer has become common in parts of Africa because of Aids, which weakens the immune system. Unlike most cancers, which begin in one place in the body and spread, Kaposi's sarcoma can start anywhere, or in several places at once. It is a cancer of the muscle, nerve and connective tissue but may initially be mistaken for breast or liver or bowel cancer, according to where it is located. Treatment is usually with chemotherapy.

Lung cancer

This is the biggest cause of cancer deaths in the world – yet it is almost 100 per cent preventable, by avoidance of smoking. In the UK, there are 38,000 new cases a year and 34,000 deaths. The rate peaked in the 1970s and has since declined by 40 per cent, as smoking declines. Rates of lung cancer are rising in the developing world as people take up smoking. Scientists predict 1 billion lives will be lost in this century due to smoking.

Non-Hodgkin lymphoma

The incidence of this disease is rising. It is a cancer of the lymphatic system. The highest rates are in North America and Australia and New Zealand. In the UK, there are 10,000 cases a year and 4,500 deaths. People with reduced immunity, as in Aids, are at increased risk. Exposure to agricultural chemicals are thought to be responsible for some of the increase.

Liver cancer

Linked with chronic hepatitis B and C, caused by viruses widespread in Africa and South-east Asia. It is also caused by aflatoxin, a mould that grows on peanuts, wheat, corn and rice. In the UK, it is rare, accounting for around 2,800 cases a year, 1 per cent of all cancers. Cancer that starts elsewhere often spreads to the liver, creating the impression that it is common. But this is not primary liver cancer. Heavy drinking leading to cirrhosis increases the risk.

Mouth cancer

The commonest cancer in India and Sudan, it is linked with chewing the stimulant betel quid. In the UK, there are about 4,700 cases a year, including cancers of the lip, tongue, mouth and throat. Smoking and drinking are the chief causes in the West.

Prostate cancer

This is the commonest cancer in men in the UK, Europe, America and Australia – and it is increasing. Nearly 35,000 men are diagnosed each year in the UK. It is rare in men under 50 and two out of three cases are diagnosed in men over 70. The disease runs in families – if you have a relative with the disease your own risk is doubled. Causes of prostate cancer are unclear. There is a PSA (prostate-specific antigen) blood test but it is unreliable and screening is not recommended in the UK. However, screening in other parts of the world probably accounts for the rise in cases. Some prostate cancers are aggressive and need surgery and/or radiotherapy and hormonal treatment. Others simply need monitoring.

Oesophageal (the gullet) cancer

This is commonest in developing countries – topping the league in Ethiopia and Kenya – but growing rapidly in the UK, for reasons that remain unclear. The rate has risen by 86 per cent among men and 40 per cent among women in the past 20 years in the UK, while it has fallen in other European countries such as France. Growing obesity may be a factor, increasing the risk of gastric reflux, potentially causing cancerous changes. There are around 7,500 cases diagnosed each year in the UK and a similar number of deaths. Drinking and smoking, especially combined, are key risks.

Stomach cancer

Japan, often touted as having the healthiest diet in the world, also has the highest rates of stomach cancer in men and, along with China, high rates in women. In Japan, very salty pickled food is popular and this is thought to account for the very high stomach cancer rate. In the UK, there are just over 8,000 cases a year, making it the eighth most common cancer. Rates have fallen thanks to the fridge – we eat more fresh food and less salty, preserved food.

Graphic and statistics from 'The Atlas of Health' by Diarmuid O'Donovan, Earthscan, £12.99. www.earthscan.co.uk