In 2015, there were 17.5 million cases of cancer worldwide and 8.7 million cancer-related deaths.
Despite the pledge of US lawmakers to wage a “war on cancer,” a 2015 systematic analysis for Global Burden of Disease Cancer Collaboration (GBD) revealed an unmet need for cancer prevention efforts, including vaccinations, promotion of a healthy lifestyle, and tobacco control.
In the 2015 GBD study, investigators sought to estimate mortality, incidence, years lived with disability (YLDs), years of life lost (YLLs), and disability-adjusted life years (DALYs) for 32 cancers in 195 countries and territories from 1990 to 2015.
To estimate cancer mortality, the investigators used vital registration system data, cancer registry incidence data, and verbal autopsy data. Cancer incidence was calculated by dividing mortality estimates through the modeled mortality to incidence (MI) ratios. To calculate cancer prevalence, MI ratios were used to model survival.
Prevalence estimates were multiplied by disability weights in order to calculate YLDs, while the YLLs were estimated by multiplying age-specific cancer deaths by the reference life expectancy. DALYs were estimated as the sum of YLDs and YLLs, according to the study.
The investigators created a sociodemographic index (SDI) for each location based on income per capita, educational attainment, and fertility. To summarize results, the countries were categorized by SDI quintiles.
The results of the study showed an estimated 17.5 million cancer cases worldwide in 2015, and 8.7 million cancer deaths. Between 2005 and 2015, cancer cases increased by 33%, with population aging contributing to 16%, population growth 13%, and changes in age-specific rates 4%.
Globally, prostate cancer was the most common form of cancer in men, which accounted for 1.6 million cases. Tracheal, bronchus, and lung cancer were the leading cause of cancer deaths and DALYs in men (1.2 million deaths and 25.9 million DALYs), according to the study.
At 2.4 million cases, breast cancer is the most common form of cancer for women. Furthermore, it is the leading cause of cancer deaths and DALYS among women (523,000 deaths and 15.1 million DALYs).
Overall, cancer caused 208.3 million DALYs worldwide in 2015 for both sexes combined. Cancer is the second leading cause of death globally.
The age-standardized incidence rates for all cancers combined increased in 174 of 195 countries or territories between 2005 and 2015. China was a notable exception, with a 12% decrease in cancer incidence, according to the study. During the same time period, age-standardized death rates (ASDRs) for all cancers combined decreased in 140 of 195 countries or territories. A large amount of countries with an increase in ASDR due to all cancers were located on the African continent.
A significant decrease in cancer deaths between 2005 and 2015 was seen for Hodgkin’s lymphoma (-6.1% [95% UI, -10.6% to -1.3%]). Although the number of cancers also decreased for chronic myeloid leukemia, esophageal cancer, and stomach cancer, the results were not statistically significant.
Despite the significant reductions in cancer mortality observed in many countries, the disease still remains a challenge for future developments. According to the study, cancer incidence is expected to increase, and will cause a strain on resources, even in countries that have advanced health care systems.
The authors concluded that controlling this threat will require an expanding arsenal of cancer prevention and treatment interventions, combined with a political commitment to address NCDs.