Using a new method for tallying the global health burden of cancer, researchers confirm that cancer rates are rising. More new cases and more lost healthy years of life occur in developing countries.
Cancer deprived people around the world of 196.3 million years of healthy life in 2013, according to statistical work published today in the journal JAMA Oncology.
Worldwide there were almost 15 million new cases of cancer and more than 8 million deaths, the study calculates.
Led by Dr. Christopher Murray, D.Phil., at the Gates Foundation-funded Institute for Health Metrics and Evaluation (IHME) at the University of Washington, the study draws on 23 years of medical and death records from 188 countries. The researchers concluded the proportion of cancer deaths among all deaths increased from 12 percent in 1990 to 15 percent in 2013.
Their statistics-heavy approach offers a new way of getting at numbers traditionally only available through the World Health Organization (WHO), which relies on governmental cancer registries. Many countries either don’t have such registries or produce low-quality data.
It may reveal cases that weren’t officially diagnosed as cancer before the patient died, for example, something that could easily happen in hospitals mostly focused on treating infectious diseases, according to Dr. Ben Anderson, a professor of surgery and global health at University of Washington, who wrote an editorial that runs alongside the IHME study.
“Using these other methods will offer an interesting comparison because maybe we’ll see some things that you don’t see through the cancer registries because the patient never gets close to a pathologic diagnosis,” Anderson said.
At the top level, the IHME numbers are largely consistent with the WHO’s.
Cancer patients generally live longer now than they did in 1990, the numbers show — yet new cases continue to mount. The study attributes rising cancer rates to an aging global population and behavioral risk factors like smoking, obesity, and diet.
Like previous global analyses of cancer, the new work finds that cancer is more common in men than women and more common in developed countries than in their poorer counterparts. All but one of the 10 most common cancers — lung, tracheal, and bronchial, or TBL — were more common in developed countries.
But looking at all types of cancer, the researchers show that 60 percent of cancer deaths occurred in developing countries. Esophageal, cervical, and oral cancers were among the more common.
But TBL cancers saw 60 percent of new cases come up in lesser developed countries.
TBL cancers were the most common type among men in 40 countries clustered in central and eastern Europe, Asia, and northern Africa, where smoking is widespread.
In regions were smoking has historically been less common, like most of sub-Saharan Africa, incidence rates adjusted for age are 5 to 10 times lower for men and 15 times lower for women than in countries with historically high smoking rates.
Another major contribution of the IHME work is its calculation of lost healthy years. Almost 70 percent of cancer-caused lost healthy time occurred in developing countries.
“The cancer registries have incidence and mortality — how many cases do we have and how many people die? Murray’s group has been trying to look at ‘What does that really mean?’” Anderson said.
Lost healthy years reveal, for example, that while breast cancer is no longer one of the most fatal cancers, it takes a heavy toll on quality of life. With 1.8 million new cases in 2013, more than any cancer other than the TBL group, breast cancer accounted for less than a third of the deaths. But it resulted in more lost years among women.
The IHME group has also looked at other causes of death around the world using the same methodology. Its numbers will allow researchers and government agencies to make apples-to-apples comparisons of which diseases affect most people in different countries around the globe.
IHME says it will update its numbers every year.