Cancer death rates have fallen steadily in the U.S. since the 1950s, a new paper in Cancer Research reveals. Kids and young adults were the first to see a big drop, but now the gains are felt by adults of all ages, the study reports.
If this sounds like a typical news flash that contradicts what you just read yesterday, it’s only because there are a lot of very similar-sounding, but different, concepts get thrown around a lot. The basic idea is straightforward. A cancer death rate measures the proportion of people (usually broken down by age) that are dying of cancer each year. And those rates are falling, according to the new research. (For example, the rate for 30- to 59-year-olds was 29% lower among people born from 1945-1954 than it was for people born three decades earlier, the paper reports.) But the death rate is, of course, different from the proportion of people who are diagnosed with cancer each year (called the incidence rate). Except for lung cancer, the researchers say, cancer incidence has remained pretty constant through the years. But if a higher proportion of 50-year-old women are diagnosed with breast cancer than were 40 years ago, that could just mean that we’ve gotten better at finding and diagnosing breast cancers — and that can even improve survival, since you can’t treat a breast cancer you haven’t found.
Finally, cancer death rates can be declining even as the number of cancer deaths increases. This is probably the most confusing point. But think of it this way: If there were a cancer that used to kill 15 people per 100,000 75-year-olds one century ago, and today it only kills 10 per 100,000, you’ll still have way more 75-year-olds dying from it today — just because there are so many more 75-years-old alive now who are at risk of dying: 0.010% of a million people is still a lot more deaths than 0.015% of 100,000 people.
So when you hear that the World Health Organization says cancer is going to overtake heart disease as the world’s biggest killer, it doesn’t necessarily mean that your odds of dying of cancer at a particular age are worse. It could just mean that cancer death rates aren’t declining as fast as other death rates are. In other words, you may now live long enough to succumb to cancer at an old age, instead of dying of tuberculosis like your great-great grandfather did.