Risks and causes of oesophageal cancer

Oesophageal cancer (cancer of the gullet - food pipe) has become more common in the past 30 years. It is the 9th most common cancer in adults in the UK with more than 8,100 cases diagnosed each year. It is more common in men than in women.

As with most cancers, cancer of the oesophagus is more common in older people than in younger. There are very few cases in people under 45 years of age.

Smoking tobacco and drinking a lot of alcohol are some of the main risk factors for oesophageal cancer in the Western parts of the world. Cigarettes contain nitrosamines and other chemicals that increase the risk of cancer. Cigar and pipe smoking also increase the risk. When you smoke, you always swallow some of the smoke as well as breathing it into your lungs.

Drinking alcohol increases the risk of one type of oesophageal cancer – squamous cell carcinoma (SCC). Smoking increases the risk of the two main types of oesophageal cancer – SCC and oesophageal adenocarcinoma. Your risk increases the longer you smoke.

If you smoke and regularly drink more than the recommended limit (3 units of alcohol a day for men and 2 units for women), your risk of squamous cell carcinoma is greater. The combined risk is greater than the risk of just smoking plus the risk of just drinking. But your risk starts to reduce as soon as you stop smoking or drinking.

Chewing tobacco or betel quid (also called paan or pan) with or without tobacco also increases your risk of cancer of the oesophagus.

Obesity means being very overweight. Body mass index (BMI) is a simple way of classifying whether people are the right weight. It looks at weight compared to height. Obesity is when a person has a BMI of 30 or higher. According to most studies, obesity roughly doubles the risk of adenocarcinoma of the oesophagus. A Cancer Research UK study published in 2011 found it causes just over 1 in 5 cancers of the food pipe (20%). This may be because obese people are more likely to suffer from acid reflux and this is a risk factor for oesophageal cancer in itself. The acid coming back up from the stomach irritates the lining of the oesophagus and over a long period of time can cause cell changes leading to Barrett's oesophagus.

A poor diet may increase your risk of oesophageal cancer. This may be due to lack of zinc, or other vitamins and minerals. If you eat a well balanced diet, with plenty of high protein foods, such as meat, fish, eggs and dairy products, you are unlikely to be short of zinc.

A diet high in fresh fruit and vegetables seems to reduce the risk of oesophageal cancer. This may be because these foods contain high levels of the antioxidant vitamins A, C and E, and folate. These vitamins, together with other substances in fresh foods, may help to prevent damage to the lining of the oesophagus that can lead to cancer. Higher levels of selenium in the blood were shown to reduce the risk of oesophageal cancer by almost 50% in a recent study. Selenium is found in all fresh fruit and vegetables, meat and eggs. But levels in foods vary widely according to the selenium content of the soil the food was grown in or that the animal grazes on.

Cancer of the oesophagus is more common in some populations in the Far East and Central Asia. It may be that the different diets eaten in these parts of the world increases the risk. Or it may be some other factor in the environment.

There is a possibility that drinking very hot drinks may increase your risk. Some studies have reported up to 3 times the risk in people who regularly drink hot drinks when they are burning hot, rather than warm. Hot drinks may damage the lining of the oesophagus, but this is very difficult to prove.

Some studies show that eating a lot of red meat may increase your risk of oesophageal cancer but a large European study (EPIC) did not find a link. So this is not clear at the moment. Some studies are looking into whether barbecued, fried or roasted meat cooked at high temperatures can increase the risk. These methods of cooking increase the content of chemicals called heterocyclic amines in food and these chemicals may increase cancer risk.

There are some other conditions that we know increase oesophageal cancer risk.  These are

• Barrett's oesophagus or acid reflux
• Tylosis - a rare skin condition
• Achalasia - a condition causing problems with the valve between the oesophagus and stomach
• Plummer-Vinson syndrome - a condition causing difficulty swallowing

Barrett's oesophagus

Barrett's oesophagus means the cells lining the oesophagus have started to change to look more like the cells lining the stomach. It is also called gastro-oesophageal reflux disease, or GORD and may develop following long term acid indigestion (acid reflux). The stomach acid comes back up into the oesophagus and irritates the lining. People with Barrett’s oesophagus are up to 125 times more likely to develop adenocarcinoma of the oesophagus than the average person. According to a Swedish study, people with long term acid reflux are at least 5 times more likely to develop adenocarcinoma of the oesophagus than average, whether they have Barrett's oesophagus or not.

Remember that the overall risk to any person of getting oesophageal cancer is quite small. The risk for adenocarcinoma with Barrett's oesophagus may be up to 125 times higher, but that is still a small risk. Every year, roughly 1 out of every 200 people with Barrett's oesophagus will go on to get oesophageal adenocarcinoma.

Tylosis

Tylosis is a rare inherited skin condition. The skin grows much too thick on the palms of the hands and soles of the feet. This condition is associated with a very high risk of squamous cell oesophageal cancer.

Achalasia

Achalasia is a condition where the valve between your stomach and oesophagus (cardiac sphincter) does not relax properly. This valve prevents food and liquids backing up into the oesophagus. So with achalasia, the lower part of the oesophagus becomes stretched and food gets stuck there. People with achalasia have a risk of both the main types of oesophageal cancer that is 10 to 11 times higher than people without achalasia.

Plummer-Vinson syndrome

This is a rare condition. People with Plummer-Vinson syndrome have anaemia (low red blood cells) due to a lack of iron. They also develop small, thin growths of tissue which block part of their food pipe, making swallowing difficult. Plummer-Vinson syndrome has been linked to an increased risk of squamous cell oesophageal cancer.

There is very little research into how occupation is related to the risk of oesophageal cancer. But a few studies show that workers heavily exposed for long periods of time to soot, metal dust, vehicle exhaust or silica dust (for example, builders, brickmasons or stonemasons) have an increased risk of oesophageal cancer. Lye, a chemical found in strong industrial and household cleaners, is also thought to increase the risk. These substances can irritate the lining of the oesophagus if they come into contact with it. If these irritants are around you, you are likely to breathe in and swallow small amounts. This increases the risk of developing oesophageal cancer.

Helicobacter pylori (HP) is a bacteria that causes stomach ulcers and can cause stomach cancer. Researchers have found that certain strains of HP may protect against adenocarcinoma of the oesophagus and infection has also been shown to reduce the risk of Barrett’s oesophagus. But HP may increase the risk of the other main type of oesophageal cancer, called squamous cell carcinoma.

Some drugs relax the valve between the stomach and oesophagus. These include drugs for Parkinson's disease called anti cholinergics, and drugs for asthma called beta agonists and aminophyllines. A relaxed valve allows acid reflux and is associated with an increased risk of oesophageal cancer. But the increased risk is quite small and has to be balanced against the benefit you get from taking these medicines for other illnesses.

People who have had radiotherapy after a mastectomy for breast cancer have double the risk of cancer of the oesophagus. This is still a small risk overall, as the risk in the general population is quite low (so double a small risk is still a small risk). The risk to you from your breast cancer if you don't have radiotherapy is much higher. Radiotherapy given after lumpectomy does not seem to increase the risk.

One UK study found a small increase in the risk of oesophageal cancer in patients who had taken bisphosphonate tablets for more than 5 years compared with a group who had not taken oral bisphosphonates. Bisphosphonates are used to strengthen bones. However, other studies have not reported an increased risk. All the studies were considered as part of a European review of bisphosphonate use and oesophageal cancer. The review decided there is not enough evidence to confirm a link and more research is needed.

Researchers have combined the results of several individual studies looking into aspirin, anti inflammatory drugs and oesophageal cancer. This is called a meta analysis and is more reliable than the results of a single study. They found that taking aspirin and other non steroidal anti inflammatory drugs (such as ibuprofen) seems to lower the risk of oesophageal cancer and also reduces the risk of oesophageal cancer for people with Barrett’s oesophagus. Researchers in 2010 reviewed a number of trials which compared people who took aspirin for at least 5 years with those who hadn't. They found that the people who took aspirin everyday for at least 5 years reduced their risk of dying from oesphageal cancer by just over a half.   

Remember that these drugs can be dangerous because they can irritate the stomach lining and cause bleeding. You should not start to take aspirin or other anti inflammatory drugs without checking with your doctor first.

One Japanese study has shown a higher risk of oesophageal cancer in people who have tooth loss. The reason for this is not clear but tooth loss can sometimes be due to poor diet or long term infection of the gums, and these factors may possibly increase the risk of oesophageal cancer too. More research needs to be done to confirm this.