Cancer is an up close and personal issue for me. In 2014, I was diagnosed with three cancers… and beat them all. Yet, almost ten million people die from cancer every year globally. It is the cause of every sixth death. Cancer is one of the largest health problems in the world. With all the cancer research conducted over the years, how is cancer mortality changing over time? Are we getting better at beating it?
Three different measures allow us to understand how the mortality of cancer has changed:
- the number of deaths,
- the death rate, and
- the age-standardized death rate.
A comparison of how these three measures have changed is shown in the graph show for global data.
Let’s look at what we can learn from each of these.
The number of cancer deaths increased by 66%
More people than ever before die from cancer – 9.6 million in the latest data from 2017.
In 1990, 5.7 million people died from cancer. This means we have seen a 66% increase in the global number of cancer deaths. This increase is what the green line in the visualization shows.
The death rate from cancer increased by 17%
But in a world with more people, we would expect more people to die. As the world population is growing the total number of deaths is rising – since 1990, the number of deaths increased from 46 million to 56 million per year.
This of course means that the number of people who did not die of cancer has also increased. To assess whether we are making progress against cancer we cannot rely on the absolute number of deaths alone. It does not account for the increase of the world population.
This is why health statisticians study the number of deaths relative to the size of the population – the death rate. It is measured as the number of cancer deaths per 100,000 people.
The red line in the chart shows that the death rate from cancer has increased by 17% since 1990. This tells us that if the world population had not increased, then instead of the number of cancer deaths increasing by 66% (as we saw above), they would only have increased by 17%. Only a quarter as much.
The difference between the steep rise in the number of deaths and the slower rise of the death rate is due to the increase of the global population.
The age-standardized death rate from cancer declined by 15%
Cancer kills mostly older people – as the death rate by age shows, of those who are 70 years and older, 1% die from cancer every year. For people who are younger than 50, the cancer death rate is more than 40-times lower (more detail here).
We would therefore expect that many more people die from cancer in an old population than in a young population. Because health is improving and fertility rates are falling, the world is aging rapidly. This impacts the change over time that we are interested in: historically, fewer died from cancer because larger parts of the population died before they reached the age when cancer becomes a common cause of death.
Epidemiologists correct for changes in age-profile over time by relying on the so called ‘age-standardized death rate’. This metric tells us what the death rate would be if the age structure of the population had stayed the same over time and would be the same across countries.1
Once we correct for both population changes and aging we get the blue line in the visualization: the age-standardized death rate from cancer. Globally this has fallen by 15% since 1990.
The world is making slow progress against cancer
Adjusted for demographic changes we find that the age-standardized death rate from cancer has fallen by 15% since 1990.
Cancer survival rates are higher in richer countries and many of these countries have achieved most progress. Specific to this study, the G7 countries fared the best in improvements.
- Italy, -28%
- Canada, -25%
- France, -25%
- United Kingdom, -22%
- United States, -20%
- Germany, -20%
- Japan, -20%
That the world is slowly making progress is also consistent with two other big trends we have studied before.
Almost a quarter of all cancer deaths are due to smoking. Since smoking rates are declining across the world (especially rapidly in rich countries where smoking was very common in the past), we see a strong decline of death rates from lung cancer rates in many countries.
Secondly, as we have shown here, the 5-year survival rates for cancers are increasing, and the research we covered suggests that this is due to both earlier detection of cancers and better treatment that increased survival.
Given the fact that cancer is one of the world’s largest health problems, a 15% improvement in 27 years does not represent roaring success. But it does show that the world is making slow progress against it.