A deadly combination of fast food, red meat and too little exercise is putting Hong Kong people at heightened risk of colon cancer which is on course to become the city's biggest cancer killer. Hazel Parry looks at what can be done to reverse the trend.

 

There is one easy way of gauging how big a killer colon cancer is in a country and that's to look for the golden arches of a fast-food restaurant, says cancer specialist Jonathan Sham Shun-tong.

If those arches are there, then it is highly likely colon cancer will be on the rise, he argues. Why? Because the existence of fast-food chains is evidence that the population of that country has adopted a Western diet, says Sham, and with it the red meat and animal fat that are known to put people more at risk to colon and rectal cancer.

In Hong Kong, as throughout Asia, the number of cases of colorectal cancer (CRC) - or bowel cancer - are on the rise, increasing by about 3 percent a year over the last 20 years. In 2008, there were 4,031 new diagnoses compared to 3,024 in 1999.

The rise in cases means bowel cancer is now the second most common cancer, accounting for 16.4 percent of all cancer new cases, and the second biggest killer causing 1,686 deaths in 2008, second only to lung cancer which killed 3,497.

But doctors and cancer experts say bowel cancer is still on the rise and unless people change their eating and lifestyle habits it will soon knock lung cancer of its number one spot to become the most common cancer and biggest cancer killer.

Sham, a specialist in clinical oncology at the University of Hong Kong, attributes the rise partly to the fact that Hong Kong is now a more affluent society. People can afford to eat more meat, their lifestyles are more sedentary and the fast foods and Western dishes rich in fat have replaced the traditional Chinese diet of rice and vegetables.

This alarming trend has also been seen in other affluent Asian cities and countries such as Singapore and Japan.

"There has been a dramatic increase in cases of colorectal cancer and basically it's down to modern city living with people eating more meat and animal fat, especially beef, less vegetables and fruit and not doing enough exercise," said Sham.

All of these factors can play a role in increasing a person's chance of developing bowel cancer, along with smoking and high alcohol intake. The risk also increases as you get older with about 90 percent of cases occurring in people over age 50. This is another reason why Hong Kong with its growing population of elderly is seeing a rise in bowel cancer cases.

His views are echoed by Yuen Siu-tsan, a medical advisor to the Hong Kong Cancer Fund and a professor from the Department of Pathology at the University of Hong Kong.

"Colorectal cancer is a cancer of a wealthy country. Wealthier countries have a high incidence rate compared to poorer countries such as African and rural China, probably because of the type of food they eat," said Yuen.

"The diet habits of people in Hong Kong have changed. We have adopted a more Western way of life and eating more meat and animal protein and less fruit, vegetables and fibre.

"When I was a child we only ate chicken at festivals such as Chinese New Year. Now people eat it every day or once a week."

Contrary to common assumptions, although men are more at risk, it is a cancer both women and men should be worried about, according to Henry Kwan Tim-lok, a specialist surgeon at Hong Kong Adventist Hospital.

"If you ask me who is at risk to this cancer, I'd say everyone who has a colon," said Kwan. "The difference is that people have different levels of risk.

"It depends on your past health, your lifestyle and your family history. If you have a family history of colon cancer, you will have a higher risk."

Around 10 to 20 percent of bowel cancer cases are due to a mutated gene which causes a condition called familial adenomatous polyposis (FAP) or a hereditary condition called hereditary nonpolyposis colorectal cancer. In both these conditions, the cancer tends to occur at an earlier age.

The remaining 80 percent or so are said to be sporadic cases and as a result are more likely to go undetected in the earlier stages when they have a better chance of responding positively to treatment.

Statistics show that cases detected in stage three when the cancer has already spread into lymph nodes and tissue close to other organs are six times more likely to relapse within five years compared to only 10 percent of those detected in stage one.

According to oncologist Sham, in most cases symptoms only occur when the cancer is in its more advanced stages of three and four which means around 50 to 60 percent of all new diagnosis result in death.

"In the early stages it is difficult to diagnose because symptoms are non specific," said Sham.

"When there are symptoms the disease is already quite well advanced and developed into a tumour which causes obstruction in the bowel leading to symptoms such as narrowing of the rectum, problem with bowel movements, blood in stools, and abdominal pain. All these are evidence of advanced disease.

"The majority of cases are diagnosed in stage three while less than 40 percent are picked up at stage one and two."

Studies have shown that bowel cancer occurs predominately as a result of cell abnormalities in the colon which start as small growths called polyps. In the majority of cases these polyps are harmless and it is believed around 50 percent of people aged above 60 will have at least one polyp of 1 cm of diameter or greater in their colon.

If left untreated a very small percentage of a specific type of polyp can grow and become cancerous.

However, this transition normally takes place over a long period of time and it is this which works to our advantage, making it a preventable cancer, says Yuen.

"The transformation from early polyp to invasive cancer takes a minimum of about 10 to 15 years so you have a long time to prevent cancer.

"If you can detect the tumour at the polyp stage it can be removed and it will not develop into cancer."

There are currently three common ways of screening for bowel cancer - all of which can detect it in the early stages before noticeable symptoms appear.

The first of these is the faecal occult blood test (FOBT) which picks up very small amount of blood produced by growths in the colon from a sample of faeces. Some countries already offer this kind of test routinely for people over a certain age but as it only detects blood it is not specific, says Yuen.

The most efficient method of screening is the colonoscopy. This involves passing a flexible tube with a camera on the end through the colon via the rectum. There is also the sigmoidoscopy but this screens part of the lower bowel and is therefore not as thorough as the colonoscopy which screens the entire colon.

Both procedures allow the doctor to look for the polyps which have the potential to develop into cancer and remove them at the same time. The procedure does carry a risk of perforating the large intestine, however, this only occurs in around one in every 1,000 cases.

"We know that most tumours pass through a stage as a polyp before they become tumours. So if an individual has regular colonoscopy and removal of polyps whenever they appear, then in theory they can prevent colorectal cancer,' said Sham.

However, in Hong Kong, the health department or public hospitals do not offer screening for bowel cancer to the general public unless they have symptoms or family history of this particular cancer.

This means any individual wishing to undergo screening has to go private with the cost of a colonoscopy ranging from around HK$3,500 to HK$7,000, plus possible extra charges for removing any polyps found.

The Centre for Health Protection has looked at the possibility of a general screening program through its Cancer Expert Working Group which published its findings last September.

The group recommended that people aged 50 to 75 should consider screening. However, it said studies had found that the knowledge and uptake of screening in Hong Kong was low which raised questions about the cost-effectiveness of a screening program and the extra burden it would place on health services.

It said the impact on the health care system of such a program first needed to be assessed.

"Taking into account the current capacity of colonoscopy, laboratory and treatment services in the public sector, screening will increase the number of people who need further management and lead to longer waiting times and delay in treatment of symptomatic cases," it said.

When questioned about screening, a Department of Health spokesman told China Daily that colorectal cancer was considered an important public health problem.

"Currently, there is still insufficient evidence to support implementation of a city-wide local screening program for colorectal cancer," he said.

In the absence of a screening programme for the general public, the experts say people should consider paying for screening at the age of 50 and then every 10 years after, stressing such action would save lives.

"You only need a colonoscopy once every 10 years which works out not that expensive," said Yuen.

"In a private setting it will cost up to HK$10,000 but if you divide that cost by 10 years, it only costs HK$1,000 a year. That's the price of dinning out for one night but it will prevent you getting colorectal cancer for the 10 years. I consider that money well spent."