In what is basically an OK article focusing on new insights about how our scientific understanding of cancers has evolved during the 40 year "war on cancer," Scientific American can't resist the scare headline, about cancer "spreading." However, the article does correctly note:
…mortality rates are in decline, falling 21 percent for men and about 12 percent for women between 1991 and 2006….
That is indeed good news. But there's even more good news which might have been mentioned—age-adjusted cancer incidence rates in the United States are also falling. That is, a lower percentage of people in various age categories are in fact getting cancer. (Cancer rates are age-adjusted because your risk of getting cancer goes up substantially the longer you live. Some researchers believe that if you live long enough you will eventually get some form of cancer. More on that below.) A study published last year in the journal CA: A Cancer Journal for Clinicians reported:
Delay-adjusted cancer incidence rates decreased by 1.3% per year from 2000 through 2006 in males and by 0.5% per year from 1998 through 2006 in females.
Why? Largely because fewer people are smoking, fewer women are taking hormone replacement therapy, and more people are getting screened for pre-cancerous colon polyps.
To illustrate the problems that cancer is causing poor countries, the Scientific American article ends:
And the disease has made serious inroads into other countries that have far fewer resources to manage it. In places where even general practitioners are few and far between, such as Rwanda, well-equipped oncologists are practically an anomaly, writes journalist Martin Enserink this week in Science. In some of the world's poorest countries about nine in 10 children diagnosed with leukemia will die from the disease, whereas in Western Europe survival is about 85 percent, he reports.
Well, yes, that is a heart-wrenching problem. But when it comes to health care problems in Rwanda, consider that according to the World Health Organization that life expectancy at birth in Rwanda is 51 years for men and 53 years for women; probability of dying before age 5 is 160 out of 1,000; the probability of dying between 15 and 60 years of age is 414 out 1,000 men and 360 out of 1,000 women.
By comparison, in the cancer-riddled United States life expectancy is 75 years for men and 80 years for women; the probability of dying before age 5 is 8 out 1,000; and the probability of dying between ages 15 and 60 is 137 out of 1,000 men and 80 out of 1,000 women.
So why would cancer be "spreading" worldwide? Chiefly two reasons: (1) the adoption of more western lifestyles, and (2) increasing life expectancy.
One prevalent hypothesis about how western lifestyles promote cancer incidence is that it leads people to become fatter and less physically active. Interestingly, there is controversy over whether eating fat boosts cancer risk or not. However, many studies suggest that eating tasty red meat increases one's chances of cancer. It turns out that as people in developing countries get richer the more meat they want to eat.
With regard to life expectancy, it is true that one way to reduce the burden of cancer in the developing world would be to do it the old-fashioned way—die young. That's probably not what people would prefer to do.