Symposium Brings Rising Global Cancer Burden into Focus
, by NCI Staff
Experts gathered last month to discuss a topic that is garnering greater attention and interest by world health groups and within the cancer community: the expanding global burden of cancer, particularly in low- and middle-income countries (LMICs).
Until recently, cancer in many of these countries has been a secondary health concern, with public health efforts focused more on communicable diseases like malaria or HIV.
But as the research presented at the NCI Global Cancer Research Symposium in Rockville, MD, made clear, that can no longer be the case. By 2030, the global number of cancer deaths is expected to skyrocket, increasing by 80% compared with recent levels. Many of these deaths will occur in LMICs.
Attendees at the meeting called for concerted action to tackle this problem head on.
“The United States has an obligation, as part of the community of man, to help other countries in their cancer control efforts,” said Barry Kramer, M.D., director of NCI’s Division of Cancer Prevention, during the symposium's keynote address.
The Tobacco Threat
The aim of the event, hosted by NCI’s Center for Global Health (CGH), was to increase opportunities for new research collaborations and strengthen existing collaborations, with a focus on cancer prevention and screening.
One area where collaborative efforts are already taking shape is tobacco control. Use of cigarettes and other tobacco products is booming in many countries. Worldwide, nearly 20% of cancer deaths and about 70% of lung cancer deaths are attributable to tobacco use, Dr. Kramer stressed. And unless this trend is reversed, he continued, cancer incidence and mortality rates in many countries will continue to rise.
Tobacco’s impact is being felt especially acutely in China, the world’s most populous country. In 2013, the average smoker in China smoked 22 cigarettes a day, a nearly 50% increase from 1980. Indeed, people in China smoked about a trillion cigarettes in 1980 and that number is now approaching 2.5 trillion.
In addition to finding ways to deter people from using tobacco products, researchers are trying to develop approaches for early cancer detection that can help reduce deaths from tobacco-related cancers.
Dr. Kramer, for example, described a collaboration in which NCI is working with Chinese health officials to conduct the ongoing China Cancer Screening Feasibility Study. A follow-up to the U.S. National Lung Screening Trial—which showed a 20% decrease in the risk of death from lung cancer with spiral CT screening compared to x-rays for heavy smokers—this study is designed to obtain the information needed for Chinese investigators to design a large screening trial in their country for lung as well as colorectal cancer, Dr. Kramer explained.
Large Role for Vaccines
Another major area of focus in reducing the global cancer burden has been increasing the use and uptake of cancer prevention vaccines. At the forefront of these efforts is expanding the availability of HPV vaccines in many LMICs, particularly those with high cervical cancer rates.
John Schiller, M.D., of NCI’s Center for Cancer Research, discussed follow-up studies from the NCI HPV Vaccine Trial in Costa Rica, which helped to establish both the safety and efficacy of HPV vaccination in preventing cervical cancer caused by several strains of HPV.
Ongoing studies, including those conducted and supported by NCI’s Division of Cancer Epidemiology and Genetics, have shown that two doses—and possibly just a single dose—of the vaccine appear to be as effective as three doses.
In fact, just weeks after this symposium, the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices altered its recommendation on HPV vaccination, saying that only two doses are needed for those younger than age 15. Many European Union countries, as well as Mexico and Canada, also currently recommend using just two doses in this age group.
As a recent report from the President’s Cancer Panel stressed, decreasing the number of HPV vaccine doses and the cost of the vaccine could be particularly beneficial in many LMICs, where limited financial resources and public health infrastructure have proven to be major barriers to administering three doses.
Dr. Schiller noted that the biological basis for vaccine efficacy is also being studied to better understand the results from some studies that have found that a single dose could be as effective as three doses.
Increasing uptake of the vaccine, he explained, could make an especially big difference in LMICs because cervical screening techniques currently used in those countries lack diagnostic precision, as is the case with visual inspection with acetic acid, and/or require extensive training of medical personnel, as is the case with Pap tests.
Collaborations between global health groups such as the Global Alliance for Vaccines and Immunization and several pharmaceutical manufacturers are also focused on securing HPV vaccines for many LMICs at a greatly reduced cost.
“If we can deliver the HPV vaccine to low-resource settings at less than $5 a dose, and possibly manufacture the vaccine in those countries, we’d see a much higher uptake of a vaccine,” Dr. Schiller said. One possibility being explored, he continued, is to express the HPV vaccine components via the existing inexpensive and widely used measles vaccine.
Meeting participants also discussed several other vaccines that may be able to contribute to reducing the global cancer burden, including those that protect against the Epstein-Barr virus (EBV) and the hepatitis B virus (HBV).
Although primarily associated with mononucleosis, EBV is responsible for an estimated 200,000 cancer deaths annually around the world, most of them in LMICs. EBV causes lymphomas and cancers of the stomach and nasopharynx.
Developing a safe and effective vaccine against EBV has proven to be difficult, but there has been some recent progress, with several trials of EBV vaccines currently ongoing.
For HBV, which is associated with liver cancer, an effective vaccine exists. But expanding use of the vaccine has been hindered by multiple factors, primarily cost and access issues. Efforts to increase access to the vaccine, symposium presenters noted, should be a priority, especially in countries where there is a high incidence of liver cancer, such as eastern and southeastern Asia.
Expanding Screening
Expanding targeted cancer screening programs is another area in which symposium participants saw potential for reducing the global cancer burden.
One high-priority effort is the International Cancer Screening Network, a program that includes 33 countries and that focuses on studying ways to improve the efficacy of screening for cancers where screening has been demonstrated to be effective, including breast, colorectal, cervical, and lung. CGH has assumed leadership for this network, which is now extending its reach to some LMICs.
“Our goal is to build on the experience of the International Cancer Screening Network countries and establish the databases and analytic approaches that will expand everyone’s understanding of cancer screening,” said CGH's Stephen Taplin, M.D.