The Global Burden of Disease Study was initiated in 1990, commissioned by the World Bank. At that time, the study was conducted mainly by researchers at Harvard and the World Health Organization (WHO). Since then the study has gone through many iterations to its present structure, which is a collaboration of more than 1,800 researchers from 127 countries. The Global Burden of Disease Study is based at the Institute for Health Metrics and Evaluation at the University of Washington and funded by the Bill and Melinda Gates Foundation. The research is intended as a tool for policymakers to weigh health-care decisions and allocate resources.
Christina Fitzmaurice, MD, MPH
To get a better understanding of the study’s recent findings, The ASCO Post spoke with one of the study’s authors, Christina Fitzmaurice, MD, MPH, a hematologist at the Oncology Clinic at Harborview. Dr. Fitzmaurice is Assistant Professor, Division of Hematology, Department of Medicine, Institute for Health Metrics and Evaluation, University of Washington. She sees patients who have cancer and also patients with benign hematologic conditions. Most of her time is spent on research efforts with the Global Burden of Disease Study.
In a nutshell, please tell the readers what the motivation was behind the analysis of the global burden of cancer?
To improve health outcomes at the population level, decision-makers need to know the burden of cancer and the individual causes. They also need to know how the burden of cancer affects populations over time at the national level. The cancer burden encompasses multiple components that are measured in incidence and mortality.
Equally important is to identify how disabling a particular cancer is. For instance, if someone is diagnosed with leukemia and has induction chemotherapy, it is considerably more disabling than, for instance, treatment of stage I melanoma, for which patients have surgery and then are finished with treatment. We also have a combined metric intended to help decision-makers look at the comparative health costs between different diseases. The measure we use is disability-adjusted life-years.
“The challenge [to reduce global smoking rates] is more difficult in middle- to lower-income countries, where the largest burden of tobacco use takes place.”— Christina Fitzmaurice, MD, MPH
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We have more than 3,000 collaborators from all around the globe who contribute data and data analysis. Although the Global Burden of Disease Study encompasses all disease issues, we singled out cancer for a special independent study because it is the second leading cause of death globally, and the incidence and mortality rates are on an upward curve. Moreover, the complexity of cancer requires a yearly updated iteration of the Global Burden of Disease Study.
Can you describe the methodology behind the study?
In this current study, we used data from the global burden of disease’s 2016 study for 29 cancer groups by sex and age and over time for 195 countries or territories. We estimated cause-specific deaths and years of life lost by age, sex, geography, and year. Years of life lost were calculated from the sum of each death multiplied by the standard life expectancy at each age. The levels and trends were analyzed over time, as well as by the Sociodemographic Index. The Sociodemographic Index contains an interpretable scale: 0 represents the lowest income per capita, lowest educational attainment, and highest total fertility rate observed across all global burden of disease geographies. Changes in incident cases were categorized by changes due to epidemiologic vs demographic transition.
The Sociodemographic Index seems to correlate well with health outcomes. Can you expand on that a bit?
Source: Global Burden of Disease Cancer Collaboration: JAMA Oncol 4:1553-1568, 2018.
This is an intriguing finding. We have found that development affects the risk factors of developing a specific type of cancer. For instance, infection-related cancers such as human papillomavirus (HPV)-associated cervical cancer, hepatitis C–associated liver cancer, or Helicobacter pylori–associated gastric cancer are less common, with improvements in development. However, if you look at lifestyle-associated cancers that are affected by factors such as obesity, diet, and lack of exercise, we see an increased risk for cancers in higher-developed regions around the world.
Efforts to Reduce Global Smoking Rates
Lung cancer continues to be the leading cause of cancer deaths. Is there a strategy to reduce smoking rates?
Yes, we have definitely made progress in that area. In 2003, WHO enacted World Health Assembly Resolution 56, which guides the tobacco control initiatives that policymakers can put into place in their respective countries. We also have big nongovernment organizations that are committed to smoking cessation, such as the Bloomberg Initiative. It has put an incredible amount of resources into developing strategies to reduce global smoking rates.
The challenge is more difficult in middle- to lower-income countries, where the largest burden of tobacco use takes place. There are multiple socioeconomic reasons for this finding, but we’re making headway in this critical issue in global health.
Moreover, after decades of research, we actually know which policies work and which ones do not work. We also know how to put them in place and get them up and running. Even though lung cancer remains the number one global cause of cancer mortality, the good news is that these programs are making a difference in reducing smoking rates.
Preventing Cervical Cancer
HPV vaccination has turned cervical cancer into a preventable disease. However, it remains one of the deadliest cancers for women in lower-income countries. What did the Global Burden of Disease Study report about this global health dilemma?
Cervical cancer was the most common cause for cancer incidence and death in countries with a low Sociodemographic Index. It is absolutely tragic that this highly preventable disease is still the number one cancer killer of women in poor regions of the world. However, there’s encouraging work taking place. For instance, the new Director-General of WHO, Dr. Tedros Adhanom Ghebreyesus, has put this health crisis on his action plan. He even talks about eliminating cervical cancer worldwide. It is a huge goal, but we have evidence that with a concerted effort, it is achievable, mainly with population-based vaccination campaigns.
“It is absolutely tragic that this highly preventable disease [cervical cancer] is still the number one cancer killer of women in poor regions of the world.”— Christina Fitzmaurice, MD, MPH
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Focus on Prostate Cancer
Globally, the odds of developing prostate cancer are 1 in 16, ranging from 1 in 56 for middle-to-low Sociodemographic Index countries to 1 in 7 in high Sociodemographic Index countries. Why is there such a disparity?
From a statistical viewpoint, the main factor is a lack of screening and early detection practices in middle-to-low Sociodemographic Index countries. Many cancers simply go undetected. However, in some low-income countries in sub-Saharan Africa, prostate cancer is among the top causes of death from cancer among men. It’s not just screening. The fact is we don’t really understand all of the drivers in the oncogenic processes in prostate cancer. Genetic susceptibility is a big factor, but it hasn’t been fully explored.
Given the comprehensive findings of this project, what is the next step to reduce the growing burden of global cancer?
Due to the world’s aging population, the incidence of cancer will increase in the future, further widening the cancer divide if current trends continue. With our growing knowledge of genetics and molecular biology, we need to look beyond the big picture and become more granular in our approaches to treating the multiple types of subgroups with one type of cancer. However, strategic investments in cancer control and implementation of effective programs are needed to ensure universal access to cancer care and to reduce the global burden of cancer. ■
DISCLOSURE: Dr. Fitzmaurice reported no conflicts of interest.