There were an estimated 18.1 million cancer cases around the world in 2020, according to the World Cancer Research Fund International. Of those cases, the United States had the fourth highest number of new diagnoses, with 362 cases per 100,000 people.
These statistics are age-standardized — a summary measure of the rate of disease that a population would have if it had a standard age structure.
Age has a powerful influence on the risk of dying from cancer, and many developing countries have a greater proportion of younger people than countries that are more developed and may have more older than younger people.
Standardization is necessary when comparing populations that differ in respects to age because otherwise countries with older populations would have vastly higher rates of cancer.
What are the countries with the highest cancer rates?
- New Zealand
- United States
- The Netherlands
What are the countries with the lowest cancer rates?
- South Sudan
- Republic of Congo
- The Republic of Gambia
Highest versus lowest:
- Australia: 452 per 100,000 people
- Singapore (lowest in the top 50): 233 per 100,000 people
- Niger (actual lowest) 78 per 100,000 people
The difficulty of tracking cancer rates
“Recording cancer occurrences and deaths is a very complex task,” says Timothy Rebbeck, PhD, associate director for Dana-Farber’s Center for Cancer Equity and Engagement and researcher in the Division of Population Sciences. “In some countries, there is a good capture of cancer rates. However, data in many countries data collection is poor, and the rate estimates rely heavily on models. These models make many assumptions. Depending on how off you are with your assumptions, you could be orders of magnitude off the actual rates.”
Rebbeck also says that the accuracy of cancer data can vary depending on the type of cancer. Breast cancer, for example is relatively identifiable, and doesn’t cause immediate death. All of this makes it easier to capture and track than a disease like prostate cancer, which might not come to clinical attention for a long time, if ever.
“In many places, the rates of prostate cancer are estimated to be very low, but that’s just because we don’t see most of them,” says Rebbeck.
Other cancers, like pancreatic cancer, has a high mortality rate, and many patients die before they are diagnosed. That information may not be recorded in the data that researchers work from.
Why do countries have low cancer rates?
The wide discrepancy in rates of cancer between the countries with the highest rates and the lowest rates is most likely due to insufficient poor data collection in developing nations. Countries like Niger and Sudan do not necessarily have lower rates of cancer; rather, these nations simply do not have the infrastructure to accurately and completely identify and register those cases.
“Some of the issue arises from the data that can be collected,” says Rebbeck. “We have numbers, but mostly — aside from places like the United States and Northern Europe — they’re not very complete.”
It’s estimated that less than 2% of the population of the entire continent of Africa is captured in the cancer data that are available, for example. In contrast, over 85% of the population is captured in cancer registries in North America.
“When you layer so many factors like healthcare access, risk factors, exposures, and prevention strategies, it is difficult to know why variations in cancer rates occur, particularly when we have limited data with which to understand these factors” Rebbeck continues,
What factors lead to high cancer rates in a country?
There are many factors that may cause higher cancer rates in a country. Many, if not all, are systemic and can be linked back to social determinants of health — the conditions in the environments where people are born, live, learn, work, play, worship, and age that affect a wide range of health, functioning, and quality-of-life outcomes and risks.
For example, “populations with better education, higher incomes and lower inequalities, active cancer control policies and programs and high performing health systems have better cancer outcomes as reflected in lower MIRs [mortality to incidence ratio] relative to other populations,” a 2019 report noted.
It is difficult to nail down exactly reasons for different rates among countries, or why Australia and the United States have higher rates versus Israel and Japan, for example. There is no single factor that can explain this difference.
“There are reasons for variation in cancer rates that we can point to, but there are other factors that we either have poor data on or don’t have a complete understanding of,” says Rebbeck.
The World Cancer Research Fund suggests that higher cancer rates are impacted by diet and lifestyle factors. For example:
- Consuming enough wholegrains, vegetables, and fruit can decrease risk of developing colorectal and prostate cancers.
- On the other hand, overconsumption of alcohol increases the risk of oral, esophageal, breast, colorectal, stomach, and liver cancers.
- Being physically active has been found to decrease the risk of colon, breast, and endometrial cancer.
“It has to do with patterns of exposure to many things like obesity, smoking, sedentary lifestyle, and a poor diet,” says Rebbeck. “Those factors are big drivers of high cancer rates. Since these exposures are changing in Africa and other regions to look more like exposures in developed nations, we can guess that cancer rates in many parts of the world will increase in the coming years.”
Risk factors can significantly impact rates of cancers across countries. Rebbeck — whose work mainly focuses on African nations — points out that people in northern Africa smoke more than people in sub-Saharan Africa. This has led to higher rates of lung cancer in northern Africa.
In some cases, high rates of certain types of cancer are also tied up in the lack of preventative measures. In the developing world, cervical cancer is a leading cause of death for women, while it isn’t a threat in places like the United States where HPV vaccines and screening measures are widely available.
However, it is again important to note that access to these diet and lifestyle choices that can reduce risk — and the ability to make changes — is not even across the board.