Global study on cancer reveals geography link

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In South Africa, for example, lung cancer, cervical and oesophageal cancer are the three deadliest in South Africa, accounting for 19,160 deaths in 2015, according to the new analysis of 32 cancer groups in 195 countries or territories. In 2015, there were 114,091 new cancer cases in South Africa and 58,237 deaths in total.

“The disease burden of cancer is growing in South Africa, and health infrastructure and resource allocation will not be capable of dealing with it unless substantial changes are made and more dedicated funding is realised,” says Professor Benn Sartorius, a co-author of the study, based in public health medicine at University of KwaZulu-Natal (UKZN) and also a steering member of the SA MRC/UKZN Gastrointestinal Cancer Research Centre.

“Initiatives such as the study allow us to track cancer trends in a timely fashion. This will continue to assist countries such as South Africa with regards to cancer burden tracking and planning as we move toward the sustainable development goals of 2030,” says Sartorius.

Increase in low development countries

The most marked increase in cancer cases between 2005 and 2015 occurred in countries of the lowest development status, where new cases grew by 50%. Authors of the study grouped countries based on their socio-demographic index (SDI) – a combined measure of education, income, and fertility. New cancer cases in the highest socio-demographic index group – including countries like the United States and Japan – grew by 36% over the same period.

In addition, cancer mortality decreased in many nations over the past decade, but increased in more than 50 countries, most of which are in sub-Saharan Africa. These countries include Niger, Kenya, Tanzania, the Democratic Republic of Congo, Mali, and Senegal, where health services needed to prevent, diagnose, and treat cancer are often missing.

In 2015, there were 17,5m new cancer cases worldwide and 8,7m deaths. The disease burden of cancer remains heaviest for countries with the highest levels of development, such as the United States, the United Kingdom, and Germany. Globally, 44% of all new cancer cases and 34% of all cancer deaths are in this highest development group.

Forms of cancer

New cases of cancer increased globally by 33% between 2005 and 2015. The most common forms of cancer globally are: breast; lung; and colorectal cancer. Lung and colorectal cancers top the list of those causing the greatest number of deaths, followed by stomach and liver cancers.

In South Africa, breast cancer is the most common cancer for women, but cervical cancer is the deadliest, with 5,406 female deaths in 2015. Other top cancer causes of death for women were breast, lung, and colorectal cancers. For men, prostate cancer fueled the highest number of new cases, but lung cancer was the number one killer, causing 5,726 male deaths. Prostate, oesophageal, colorectal, and liver cancers were the other leading causes of cancer death for South African men.

Death rates per 100,000 people are rising for the top 10 causes of cancer death in South Africa, with the exceptions of oesophageal and stomach cancer. The most marked increases were displayed by colorectal cancer, with a death rate that rose 31% between 1990 and 2015; breast cancer, which grew 35%; ovarian cancer, up 41%; and the death rate of prostate cancer increased by 45%.

Diverse types of cancer also afflict countries very differently. For example, cervical cancer was ranked the 20^th leading cause of death in the United States in 2015; in neighbouring Mexico, however, cervical cancer was ranked significantly higher at number eight, with twice the mortality rate. In South Africa, a significantly lower-resource setting, cervical cancer was the second leading cancer killer, claiming the lives of 5,400 women in 2015.

Straining the healthcare system

The authors of the study call on government agencies and the private sector to expand prevention efforts, especially in lower SDI countries where several of the deadliest cancers, such as cervical and liver cancer, are also the most preventable. For example, chronic hepatitis B and C are responsible for the majority liver cancer deaths, viruses that are preventable. However, in low-SDI countries where childhood immunisation to hepatitis B is not universal,
incidence of liver cancer has increased since 2010. Countries where liver cancer tops the list of top cancer killers include Nigeria, Ghana, Egypt, and Thailand.

“The cancer divide is real and growing,” says lead author Christina Fitzmaurice, assistant professor at the Institute for Health Metrics and Evaluation (IHME) at the University of Washington. “The number of new cancer cases is climbing almost everywhere in the world, putting an increasing strain on even the most advanced health systems. But the most rapid and troubling escalation can be seen in countries of lower development status, which can ill afford it.”

The report was published today in JAMA Oncology in a study by the Global Burden of Disease collaboration, an international consortium of 2,000 researchers in nearly 130 nations led by IHME.