Cancer's global death toll is expected to increase at an "alarming pace" over the next two decades, rising to 22 million new cases and 13 million deaths per year.
That's the message of a new report from the International Agency for Research on Cancer (IARC), the arm of the World Health Organization that tracks cancer's spread and releases fresh figures on the disease every five years.
The latest edition, based on statistics from 2012, estimates that 60 per cent of new cancer cases and 70 per cent of cancer deaths happen in the developing world, reinforcing the divide between rich and poor nations. In some well-off Western countries, you're likelier to get cancer. In less-developed countries, cancer is likelier to kill you.
Denmark, France, Australia, Belgium and Norway recorded the highest incidence of new cancers (excluding non-melanoma skin cancer) in 2012, but all five plunged down the list when it came to cancer mortality. Canada followed a similar pattern, placing 12th in cancer incidence, with about 295 new cases for every 100,000 people and 64th in mortality, with about 103 deaths per 100,000.
The countries with the highest cancer mortality rates in 2012 were Mongolia, Hungary, Armenia, Serbia and Uruguay.
Lung cancer remains the most common – and deadliest – cancer in the world, with an estimated 1.8 million new cases and 1.59 million deaths in 2012. It affects and kills more men than women around the globe, but the trend lines for the genders are diverging: The numbers have generally been going up for women and down for men.
Why? “When you’re looking at cancer statistics, it’s like looking at light from a distant star,” explains Eduardo Franco, chair of the department of oncology at McGill University’s faculty of medicine. To understand the disease pattern, epidemiologists study how people behaved two or three decades ago, when cancers blooming today would have taken root.
In the case of lung cancer, tobacco companies began aggressively targeting women in the 1970s. “Eventually rates of smoking in women started picking up,” Dr. Franco says.
Historic smoking rates also help explain why the incidence of lung cancer among men is highest in Central and Eastern Europe, where the IARC documented 53.5 new cases per 100,000 people in 2012, and lowest in West Africa, where only 1.7 new cases per 100,000 were logged. (Canada is in the middle of the pack, with 37.9 new cases per 100,000.)
“If you live on a dollar a day, you probably don’t smoke,” says Mary Gospodarowicz, medical director of the cancer program at Toronto’s Princess Margaret Hospital, explaining West Africa’s paucity of lung cancer. That, however, is changing as people in Africa and elsewhere in the developing world move out of abject poverty and into cigarette companies’ sights.
“The reason for promoting tobacco control is to prevent the looming cancer epidemic in Africa,” she adds. “Those countries are least prepared to deal with it. They practically have no viable health-care system.”
Cancers that begin in the liver are among the deadliest: Liver cancer is the second-most common cause of cancer death around the world, even though it strikes far fewer people than other types of cancer.
Most of those people are dying in Asia, where hepatitis B – which can lead to liver cancer – is rampant in some countries. Mongolia, Laos, Vietnam, Cambodia, Thailand and China are among the top 10 countries for liver-cancer deaths, according to the IARC.
Mongolia had the highest overall cancer mortality rate of any country in the world, with 161 deaths per 100,000 people, and liver cancer is largely to blame.
According to an April, 2011, article in The Lancet medical journal, hepatitis B and C are common in Mongolia, a sprawling rural country with little in the way of modern health care. “Alcohol use, which hastens progression to cirrhosis for those with concurrent viral infection, is also widespread in Mongolia, compounding the epidemic,” The Lancet wrote.
In 2012, about half of the 782,000 new liver cancer cases occurred in China. However, those figures are expected to improve in the next generation or two.
“There’s now a universal vaccination – a hepatitis B vaccination program in China,” Dr. Gospodarowicz says. “They vaccinate infants after birth immediately.”
Canada logged 3.6 new cases of liver cancer and 3.3 deaths per 100,000 people in 2012.
Breast cancer is the most common cancer in women, with an estimated 1.7 million new cases in 2012 and 522,000 deaths around the world. Those figures have risen 20 per cent and 14 per cent, respectively, since 2008.
Why the increase? Excellent screening in rich, developed nations is one reason; the trend toward bearing few children beginning later in life is another.
“By delaying childbearing, or even forgoing completely bearing children, [women] increase their risk of breast cancer,” Dr. Franco says.
The pattern of new breast cancer diagnoses and deaths in 2012 shows again that, when it comes to cancer, geography is destiny. A woman is much more likely to be diagnosed with breast cancer in Western Europe (90 new cases per 100,000 women) than in East Africa (30 per 100,000 women), but she’s equally likely to succumb to her illness in both regions.
“The reason why mortality is the same is [that] while we have early detection and effective screening and treatment programs in Europe and North America, these programs are totally non-existent in Africa,” Dr. Gospodarowicz says. “In fact, because of stigma and because of lack of resources, [women] don’t even tell anybody they have a lump in the breast until they have huge ... masses, bleeding, very, very extensive cancers, something we don’t see in developed countries any more.”
The countries with the highest proportion of new cases in 2012 were in Western Europe – Belgium, Denmark and France topped the list – while those with the highest mortality rates were Fiji, the Bahamas and Nigeria. Canada recorded 79.8 new cases and 13.9 deaths per 100,000 women.
Prostate cancer was the most frequently diagnosed cancer among men in Canada in 2012, with 88.9 new cases for every 100,000 men.
But when it comes to mortality, prostate cancer drops to third, killing an estimated 9.4 per 100,000 men in 2012.
Canada’s figures mirror what is happening with prostate cancer in the rest of North America and Europe, where widespread use of the prostate-specific antigen (PSA) blood test has made early detection and treatment of prostate cancer common. In fact, the aggressive testing campaigns have raised concerns that prostate cancer is being overly diagnosed, leading men to undergo surgery for a cancer that might never grow to affect their health.
Prostate cancer is deadlier elsewhere in the world, particularly in the Caribbean, where it killed 29 per 100,000 men in 2012, and in sub-Saharan Africa, where it killed as many as 24 per 100,000 men the same year.
“It’s one cancer that happens a lot, and we have no idea what causes it,” Dr. Franco says.
Cervical cancer is the fourth-most common cancer in women, with an estimated 528,000 new cases and 266,000 deaths in 2012.
For women in the developing world, it’s especially prevalent – and especially deadly. Compare the toll cervical cancer takes in parts of East Africa, where it killed an estimated 27.6 per 100,000 women in 2012, to the toll it takes in Western Europe, Australia and New Zealand, where the disease killed an estimated two per 100,000 women the same year.
The chasm can largely be explained by modern screening – regular Pap smears – and modern treatment, or the lack of it. In parts of Africa, “there’s absolutely no screening, no early detection and tremendous death rate,” says Dr. Gospodarowicz, who is also the president of the Union for International Cancer Control.
The sexual habits of a population play a part, too. Most cervical cancers are caused by the human papillomavirus, or HPV, a sexually transmitted disease.
Several of the countries least afflicted by cervical cancer have Muslim majorities with conservative sexual mores, including Egypt, Jordan, Saudi Arabia and Iran, all of which logged cervical cancer mortality rates of 1.2 per 100,000 women or lower in 2012.
Canada recorded an estimated 6.3 new cases and 1.7 deaths per 100,000 women in 2012.
Iceland boasted the lowest cervical cancer mortality rate of all: 0.4 per 100,000 women. Finland was not far behind with a rate of one death per 100,000 women.
“The Finnish are having a lot of fun in their lifestyle,” Dr. Franco says. “They have everything that’s conducive to transmission of HPV but they cancel this out by having the best cervical-cancer screening program in the world.”
Women in much of Africa are not so fortunate. Malawi and Mozambique, for example, recorded cervical cancer mortality rates of more than 49 per 100,000 women in 2012, the highest in the world.
Dr. Gospodarowicz says there is hope the HPV vaccine could bring that death toll down for the next generation, especially if the systems created to deliver anti-retroviral drugs to poor villagers with HIV and AIDS are used to vaccinate young women against the virus that causes cervical cancer.
“Because of these distribution channels,” she says, “it is expected that we will be more successful in HPV vaccination than maybe other anti-cancer interventions in Africa and other countries.”
Graphics by Tonia Cowan/The Globe and Mail
Note: The numbers used are age-standardized, which means they show the incidence rates if that population has a standard age structure.
Source: Globocan 2012 (International Agency for Research on Cancer)