Every sixth death in the world is due to cancer, making it the second leading cause of death (second only to cardiovascular diseases).1 In 2016, 8.9 million people are estimated to have died from the various forms of cancer. The Institute for Health Metrics and Evaluation (IHME) put relatively small error margins around this global figure: the lower and upper estimates extend from 8.75 to 9.1 million.2 Progress against many other causes of deaths and demographic drivers of increasing population size, life expectancy and — particularly in higher-income countries — aging populations mean that the total number of cancer deaths continues to increase. This is a very personal topic to many: nearly everyone knows or has lost someone dear to them from this collection of diseases.
In advance of World Cancer Day (on February 4th), in this short blog post we present a global overview of cancer deaths — how these vary by cancer type, age, and how the incidence of cancer deaths is evolving. Whilst we largely focus on the global pattern of cancer deaths, all of the data presented here – based on estimates from the IHME's Global Burden of Disease programme – is available to explore by country using the "change country" function at the bottom of the interactive charts which follow.
Cancers are defined by the National Cancer Institute (NCI) as a collection of diseases in which abnormal cells can divide and spread to nearby tissue. As this definition suggests, cancers can arise in many parts of the body (leading to a range of cancer types, as shown below) and in some cases spread to other parts of the body through the blood and lymph systems.
In the chart below we see the total number of deaths in 2016 attributed to the range of cancer types. With more than double the number of attributed deaths of the next leading form, 'tracheal, bronchus, and lung cancer' claimed the largest number of lives at more than 1.7 million in one year. Next follow 'stomach cancer', 'colon and rectum cancer', and 'liver cancer', all with a similar number of deaths, at around 830,000 globally in 2016.
This chart also allows exploring deaths by country (click 'change country' at the bottom of the chart).
In exploring patterns across various countries, we see that 'tracheal, bronchus, and lung cancer' is the leading form of cancer deaths across most high and middle-income countries. However, the leading form in lower income countries varies: colon and rectum; liver; cervical; stomach; breast and prostrate all top the list in several countries.
If we look at how the number of cancer deaths has changed since 1990 — as in the chart below — we see that global deaths have increased from around 5.7 million to 8.9 million over this period. Note you can scroll over this chart to see the annual number of deaths by type over time. For clarity, we have grouped all cancer types with less than 100,000 global deaths in 2016 into a collective category 'Other cancers'.
If we switch the chart below to "relative" mode we can compare how the distribution and share of deaths across the various cancer types has changed since 1990. With just under 20 percent of the total, 'tracheal, bronchus and lung cancer' have the highest share at the global level. Overall, we see that the relative share of deaths across cancer types has remained largely stable with time. Some notable changes occurred in stomach cancer (which has fallen from 13.8 to 9.4 percent); esophageal cancer (falling from 5.7 to 4.7 percent); liver cancer (rising from 8.2 to 9.3 percent); and pancreatic cancer (rising from 3.6 to 4.6 percent).
How are cancer deaths distributed across age groups?
In the chart below we see the breakdown of total cancer deaths by broad age category, ranging from under-5s to those over 70 years old. Overall, we see that the majority of cancer deaths occur in those over 50 years old; 44 percent of cancer deaths in people aged 70+ years old, closely followed by 43 percent aged between 50 and 69. The distribution of deaths across the age spectrum has changed notably since 1990; the share of deaths which occur in those aged over 70 has increased by 7 percent, whilst the share in those aged 50-69 and 15-49 has fallen by approximately 3-4 percent each.
Collectively, children and adolescents under 14 years old account for less than one percent of cancer deaths — although still tragically, this equates to around 80,000 children per year.
With an increase in global cancer deaths from 5.7 to 8.9 million since 1990 (an increase of 56 percent), and similar trends in the number of absolute deaths across most countries, it may seem reasonable to assume that cancer death rates are on the rise. But is this really the case?
Whilst a crucial metric of total disease burden and mortality, the absolute number of deaths has two key caveats: it fails to account for changes in population size and age structure. As we have explored above, the majority of cancer deaths occur in those aged over 50 years old; this means we should expect the total number of cancer deaths to increase as a population ages. The drivers of rising life expectancy, aging populations, and population growth can compound to give a skewed perception of frequency.
A more useful metric in this regard is the age-standardized death rate. This metric corrects for the effects of changing age distributions by normalising to a fixed reference population structure (assumed the same across countries and with time), and for differences in population size by reporting as the number of deaths per 100,000 individuals.3 The age-standardized death rate from all cancer types are shown in the visualisation below. This data can be explored through time using the 'play' button at the bottom of the chart, and national time-series can be viewed by clicking on a respective country.
In 2016, we see that most countries have death rates of 50 to 150 deaths per 100,000 individuals. On average, higher-income countries tend to fall towards the upper band of this range; across North America, Europe, and Australasia, rates are typically close to 150 per 100,000. This is also true across a number of countries in Sub-Saharan Africa. Rates across Latin America, Asia, and some parts of Africa are on average lower (50-125 per 100,000).
If we use the timeline to see how death rates have changed since 1990 we see that rates have fallen significantly across a large share of countries. In the United States and Canada, rates have fallen from over 180 in 1990 to below 150 per 100,000; in the 1990s, Russia peaked at over 200 per 100,000 and has since fallen below 150; and China has seen a similar size of decline since 1990. This is not true everywhere: rates have risen across some countries, including South Africa and India. Age-specific death rates, in comparison to all age and age-standardized rates can be explored here.
The overall global trend nonetheless shows an often counter-intuitive finding: despite increasing numbers of cancer deaths, individual death rates are falling. In 1990, 161 people out of every 100,000 globally died from cancer — by 2016 this had fallen to 134 per 100,000.
For the purposes of assessing the total incidence of cancer, in the chart above we grouped all cancer types together to look at overall trends. However, death rates and progress in reducing mortality incidence varies across the many forms of cancer. In the chart below we see the individual age-standardized death rates across cancer types. This is again measured as the number of deaths per 100,000 individuals.
As we would expect from the leading cause of cancer deaths, rates in tracheal, bronchus and lung cancer are highest globally at 26 per 100,000. This has fallen slightly from approximately 29 per 100,000 in 1990, with even greater declines in some countries (in the US, rates have fallen from 53 to 41 per 100,000).
In some cases we have seen dramatic declines over the last few decades. The most notable is stomach cancer, for which death rates have fallen by more than 40 percent from 22 to 13 per 100,000. Rates in esophageal and cervical cancer have also both dropped by around one-third since 1990.
The overall global trends on cancer mortality — as summarised in data above — tells a story which at first glance can seem conflicting.
The total number of deaths from cancer is increasing. This is predominantly a result of aging (and growing) populations. Once we correct the number of deaths for population size, we see that cancer death rates have approximately flatlined; then when further corrected for age we see that globally, death rates are falling. This represents progress, although very slow.
Although not the focus of this blog post (which has focused on cancer deaths), survival rates introduce another metric of progress. Here, we have seen significant developments in recent decades. In the United States, for example, the five-year survival rate across a range of cancer types has increased significantly over the past 20-30 years. Cancer continues to claim the lives of many, but we are perhaps slowly moving in the right direction.