The next World Cancer Report is currently in preparation and will be published later this year. Hundreds of prominent investigators worldwide are contributing as authors or reviewers. World Cancer Report is published by the International Agency for Research on Cancer (IARC) about every 5 years.
IARC Director Dr Elisabete Weiderpass and former IARC Director Dr Christopher P. Wild are co-editors of the upcoming World Cancer Report, along with Dr Bernard W. Stewart.
Dr Weiderpass and Dr Wild responded to important questions on strategies to address the growing worldwide burden of cancer and about how individuals and public health professionals can face the challenges of cancer control in high-, middle-, and low-income countries.
Dr Elisabete Weiderpass answered some questions about the upcoming World Cancer Report.
1. Why is prevention the only option to tackle the growing burden of cancer, particularly in low- and middle-income countries?
The current burden of cancer is notably higher in low- and middle-income countries, because of the disparity in incidence and mortality rates between high-income countries and low- and middle-income countries. Although high-income countries have overall higher cancer incidence rates, cancer mortality rates and total mortality due to cancer are significantly higher in low- and middle-income countries, where 70% of all deaths from cancer occur.
The prediction is for the cancer burden to get even worse in low- and middle-income countries, because cancer incidence rates are rising in those countries, mainly due to improvements in life expectancy and changes in lifestyles. The best option to change this scenario would be investment in initiatives for primary cancer prevention (to lower the risk of cancer) and secondary cancer prevention (screening and early detection), because the infrastructure and investment needed for improvements in cancer treatment are more complex, more costly, and less efficient in dealing with this disparity.
2. What are the most promising strategies in terms of cancer prevention?
In the arena of primary prevention, we have the European Code Against Cancer, an initiative of the European Commission, developed by IARC, that aims to inform people about actions they can take for themselves or their families to reduce their risk of cancer. The current, fourth edition consists of 12 recommendations that most people can follow without any special skills or advice. It has been estimated that potentially up to 40% of the new cases of cancer in Europe could be avoided if everyone followed the recommendations. IARC is now leading the adaptation of the European Code Against Cancer to low- and middle-income countries; a specific recommendation for Latin America is under discussion.
With respect to secondary prevention (screening and early detection), in 2018, the Director-General of the World Health Organization (WHO) announced a global call to action towards the elimination of cervical cancer, underscoring renewed political will to make elimination a reality, and called for all stakeholders to unite behind this common goal. A comprehensive strategy was designed that includes action on advocacy, mobilization of civil society, health economics, increasing access to health care, vaccination against human papillomavirus (HPV), screening, treatment, monitoring, surveillance, and research. This initiative became a flagship project of WHO, and IARC is playing an important role in many of these actions.
There is also the WHO publication on the “best buys”, the recommended interventions for the prevention and control of noncommunicable diseases in low-resource settings, which include interventions for cervical cancer and breast cancer. Moreover, innovative and culturally adapted strategies for cancer prevention, screening, and early diagnosis should be considered as priorities for implementation of research projects in low- and middle-income countries.
3. What are the challenges in terms of implementing efficient prevention strategies?
There is now more and more research on the influence of health inequalities on the cancer continuum. IARC has just summarized the current scientific evidence and identified research priorities needed to decrease social inequalities in cancer in the IARC Scientific Publication Reducing Social Inequalities in Cancer: Evidence and Priorities for Research. The publication, based on the expert knowledge of more than 70 international scientists from multiple disciplines, undertakes a populations-within-populations approach, highlighting the large variations in cancer incidence, survival, and mortality that exist between countries and, within countries, between social groups. Several factors may lead individuals with low social status to adopt unhealthy behaviours, to be exposed to a wider range and a higher intensity of cancer risk factors, and to have reduced access to health-care services, compared with their fellow citizens. A special focus is given to how the phenomenon of inequalities in cancer evolves and is reshaped over time, driven by economic, social, political, legislative, and technological forces; it affects everyone, but the most disadvantaged individuals are particularly hard hit. This IARC Scientific Publication was developed to serve as a reference for policy-makers and public health officials, linking to specific examples of interventions that may reduce future inequalities in cancer.
Finally, to be cost-effective and to ensure that the benefits outweigh the harms, cancer prevention programmes and initiatives need to be evidence-based. Research is fundamental for this achievement, and that is one of IARC’s missions. Nevertheless, more investments in cancer research are needed, particularly in low- and middle-income countries; as Mary Lasker once said, “If you think research is expensive, try disease”.
Dr Christopher Wild answered some questions about the upcoming World Cancer Report.
1. Identifying agents that cause cancer is one aspect of cancer prevention research, which also includes the study of susceptibility, mediators of cancer development, and early detection. What about prevention strategies for those tumour types for which external causative agents have not been identified?
Without identification of risk factors for a given cancer type, there is no basis for primary prevention. Examples of common cancers where this is still the case are prostate cancer, brain cancer, pancreatic cancer, and haematological malignancies. Here, there is a strong case to enhance research to identify risk factors through epidemiological and experimental studies, including a consideration of mechanisms of action other than through induction of mutations.
At the same time it is vital to seek ways of identifying the above-mentioned types of cancers early, to improve treatment outcomes. Such efforts should use advances in cancer biology to understand underlying molecular changes that may serve as biomarkers of risk. Surveillance or screening programmes might be targeted to the people at highest risk, based on their genetic makeup, environmental co-exposures, or comorbidities. In these groups of high-risk individuals, medical prevention or chemoprevention may be an option, if the benefits can be demonstrated to outweigh the risks of such approaches.
2. Some countries do not face a burden of obesity-related cancers. Why is that, and what can be learned from this?
Obesity and overweight have tended to occur when a population shifts to an industrialized environment and lifestyle. Urbanization, less physically demanding jobs and lifestyles, and a shift in diet result in an energy imbalance, favouring weight gain. Different regions and countries are at different stages of this epidemiological transition, and therefore many have not yet experienced the full effects of rising obesity rates. Although obesity and overweight are major risk factors in countries with high and very high levels of the Human Development Index (HDI), this is not the case in the majority of countries with medium and low HDI levels. Notwithstanding those national differences, populations in urban areas of countries that still have low HDI levels are already experiencing rises in obesity rates in adults and children.
The wide geographical variation in rates of obesity and overweight offers two opportunities. The first concerns cancer control. Countries that have not yet succumbed to the obesity epidemic can seek to avoid repeating the mistakes of the countries that are feeling its full effects. Regulatory measures including fiscal policy, education, and public health initiatives may all be invoked. The second concerns cancer research. Countries in transition offer great opportunities to understand how obesity and the underlying drivers affect cancer and to test preventive interventions aimed at avoiding the obesity epidemic rather than reversing it.
3. Reducing pollution of air, water, soil, and food could have a significant impact on cancer incidence. How can this objective be reached?
There are risk factors over which individuals have a degree of control. Avoiding or limiting exposures, for example to alcohol or excess sunlight, by adopting specific behaviours has a significant impact on an individual’s cancer risk. At the same time, exposure to the same factors may be strongly influenced by the regulatory context in which individual choices are made. For example, higher pricing of cigarettes reduces consumption, and state support to individuals trying to quit smoking assists the behaviour change being sought. Thus, policy can enable positive choices to reduce cancer risk.
However, there are areas, such as pollution of air, water, soil, and food, where it is extremely difficult or impossible for an individual to significantly control their exposure to harmful substances. In these areas, regulatory policy is needed, often at the international level rather than only at the national level. In these instances, the role of individuals may be to band together to demand change from their political leaders. In any case, it will most often be a combination of regulation, information, and education that is required to achieve effective cancer control.