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Study reveals higher rates of colorectal cancer in more developed countries
Increased disparity has led to a 10-fold difference in numbers of cases worldwide
Economic development is a good thing – but not when it comes to the risk of developing colorectal cancer.
According to a recent study, as a country develops, rates of this type of cancer rise alongside it.
The study revealed a 10-fold difference in cases worldwide, based on a country’s level of economic development. The “western” lifestyle that comes with a country’s growing economy is thought to be behind the increase in rates.
“Colorectal cancer is the clearest marker of societal and economic transition,” says Cancer epidemiologist Melina Arnold, from the International Agency for Research on Cancer, who led the study.
Also known as bowel cancer, it’s the third most common type of cancer in the world. It affected 1.4 million people in 2012 and is predicted to increase by 60%, to more than 2.2 million cases – and 1.1 million deaths – by 2030.
This form of cancer is a common result of poor lifestyle choices such as a bad diet, low levels of exercise, smoking and drinking excessive alcohol.
“[It] is largely preventable because it’s related to lifestyle factors,” says Arnold.
Arnold and other experts in the field were already aware of the geographical variation seen in rates of this cancer specifically, but its extent came as a revelation.
“There is a widening disparity,” says Arnold.
Does prosperity lead to cancer?
Arnold’s team analyzed rates of colorectal cancer across all levels of the Human Development Index (HDI) in 184 countries and found that the higher the HDI, the higher the rates of bowel cancer. Countries with a very high HDI had levels, on average, six time higher than countries with a low HDI.
More importantly, this type of cancer was found to be on the rise in low and middle-income countries as their economies develop.
“Decades ago you didn’t see so much of it in low-income countries, there were more infection-related cancers,” says Arnold.
One example of an infection-linked cancer is cervical cancer, which can result from infections with Human Papilloma Virus (HPV).
But today, lifestyle diseases – and cancers – are making more of an appearance.
“Low income countries are catching up,” she says.
Countries where colorectal cancer numbers – and death rates – were on the rise, or stable, include China, Russia, Brazil and the Baltics, which have all undergone rapid economic development over the past decade. With this change comes rapid progression to a western diet and lifestyle.
The study was observational, with findings based on populations aging and living longer, but experts have long known the role of lifestyle in the onset of this form of cancer.
Lifestyle and cancer
“There is a prominent role of diet and lifestyle in this cancer,” says Amanda Cross, Assistant Head of the Cancer Screening and Prevention Group at Imperial College London.
Cross researches the role of red meat and processed meats in the development of this form of cancer. “Those that consumed the most meat did have a higher risk,” says Cross. This finding was again observational.
Excess consumption of red meat, however, often comes with other poor lifestyle choices that also impact the chances of developing this cancer. “People who tend to eat the most red meat tend to be more overweight and are less active,” says Cross.
Men are at greater risk of the disease, but reasons for this trend are not fully understood.
How it develops
“Bowel cancer is a slow growing disease and the symptoms only develop at a later stage,” says Christian Von Wagner, an epidemiologist at University College London (UCL).
Symptoms mainly affect the bowel and abdomen region and include blood in faeces, pain in the abdomen or back passage, or lumps in that same region.
Without standard screening programs in place within affected populations, the cancer is often found too late, leaving only a 10% chance of surviving the next five years.
“Once symptoms have developed, it’s likely the cancer will have spread,” says Von Wager.
The key therefore is early detection and increasing opportunities for screening in all affected countries and not just the affluent ones as, according to Cross, 90% of people will survive five years if diagnosed early.
Detection and prevention
“Something needs to happen in countries seeing this transition where there is increased burden,” says Arnold. “Early detection is important and drives down the mortality.”
Today, screening is possible through both home testing kits as well as the more traditional sigmoidoscopy to examine inside the colon.
Primary prevention is also key, through increased awareness and healthier lifestyle choices, This, in turn, would benefit other disease epidemics, such as obesity and diabetes.
Obesity is known to be linked with colorectal cancer.
Risk can also be reduced by including more fiber in the diet.
“There are a lot of modifiable factors that contribute to this disease…people who eat the most fiber have the lowest risk,” says Cross.
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According to World Cancer Fund International, in countries like the UK an estimated that 47% of colorectal cancer could be prevented by eating and drinking healthily, being physically active and maintaining a healthy weight.
Resources now need to be targeted within the countries that need it.
“It’s important to see geographical trends and variation in order to plan cancer control,” says Arnold.