For the researcher: what’s exciting about the new World Cancer Report
The global cancer burden and its causation
World Cancer Report: Cancer Research for Cancer Prevention features the latest research from across multiple disciplines. The impact of cancer on the global community can now be defined with greater precision than ever before. Population-based cancer registries operate in many countries, and data from hospitals and other sources provide a clear indication of cancer incidence and mortality in most other countries.
Some of the tumour types that account for most cancer-related morbidity and mortality in particular countries may now be attributed to particular carcinogens. Although this approach remains vital, the science now addressed in World Cancer Report is more broadly based and particularly concerns relevant biological mechanisms of carcinogenesis.
Understanding the global cancer burden depends on far more than numerical data for particular tumour types. Among other key factors, it involves appreciation of the impact of socioeconomic transition worldwide as this affects different world regions. The causes of cancer, for many tumour types, have been well known for decades but are now better understood in terms of both the precise biological changes induced by causative agents and the characteristics of exposed people who prove to be susceptible to cancer development. This is the broad background against which both biological and sociological variables determine the distribution of cancer and, in many instances, its potential prevention.
Factors determining cancer development and prevention
The causes of cancer vary markedly in their character and impact. Cancer is just one of the diseases caused by tobacco smoking, but lung cancer and other cancer types caused by smoking are among the most lethal of such diseases. Millions of people are infected with human papillomavirus (HPV), Helicobacter pylori, or hepatitis B virus or hepatitis C virus, and are thus at risk of developing cervical cancer, stomach cancer, and liver cancer, respectively. Complex biological processes, including DNA repair, the occurrence of overweight or obesity, and the consequences of inflammation, are crucial determinants of cancer development. These processes are delineated in the new World Cancer Report.
Although much is known about cancer causation, for many tumour types few, if any, relevant carcinogens have been identified. This applies to, for example, brain cancer and prostate cancer. For lung cancer, a broad spectrum of causes are known, beginning with active smoking and extending to second-hand smoke, certain occupations, and atmospheric pollution. Despite this, some individual cases of lung cancer have no evident cause. Such tumours, along with most cases of brain cancer and prostate cancer, are often described as sporadic. An exciting first for the new World Cancer Report is a discussion of sporadic cancer and the biological principles that are thought to underpin the development of such cancer.
Biological processes are common to all people, but the distribution of cancer in all countries is subject to socioeconomic differences. For the first time, inequalities as a determinant of cancer incidence and mortality are specifically addressed in a separate section of the new World Cancer Report. Previous World Cancer Reports described the disproportionately increasing burden of cancer in low- and middle-income countries, and this trend clearly persists. However, in all countries, irrespective of income grouping, sections of the communities are disadvantaged both in relation to circumstances of risk and with respect to prevention and treatment services. In the new World Cancer Report, separate chapters evaluate inequalities that affect cancer incidence in Africa, China, Europe, India, and the USA.
Increasing options for cancer prevention
Cancer prevention is often identified with community campaigns, such as those to promote smoking avoidance or cessation, to ensure that exposure to asbestos does not occur in the workplace and elsewhere, to prevent particular infections, and, particularly for fair-skinned people, to avoid deliberate sun exposure without sun protection. All these ways of preventing cancer remain relevant; they are proven to reduce cancer incidence, and research continues to demonstrate their efficacy. However, cancer prevention involves a far greater range of initiatives than avoiding exposure to known carcinogens. Perhaps the most effective means of cancer prevention, and one that has the prospect of eliminating one tumour type completely, is vaccination against human papillomavirus (HPV), which is the cause of cervical cancer. Vaccination against hepatitis B and C viruses also has a proven impact on the incidence of liver cancer in certain communities.
The single greatest challenge to cancer prevention identified in the new World Cancer Report is overweight or obesity. Although the prevalence of overweight or obesity is readily identified with populations in high-income countries, this condition is now evident in many regions of the world. Multiple tumour types, including colorectal cancer and breast cancer, are attributable, at least in part, to overweight or obesity. The biological mechanisms by which overweight or obesity increases the risk of various tumour types are not yet fully explained. Altering community behaviour to reduce the prevalence of overweight or obesity is recognized as a means of preventing not only certain types of cancer but also other chronic diseases such as type 2 diabetes.
For sporadic cancers in different organs (i.e. cancers for which no recognized exposure accounts for tumour development), options for prevention are emerging and are being evaluated by researchers. For multiple tumour types, World Cancer Report discusses population-based screening for detection of cancer at an early stage or of preconditions leading to cancer development. One chapter describes early diagnosis on the basis of tumour DNA detected in blood, and another describes how individual susceptibility to tumorigenesis may be determined using genomic data.
Specifying what’s Fundamental for every chapter
The new World Cancer Report centres on research activity during the past 5 years. More than 60 different chapters each address a topic relevant to cancer prevention. The chapters do not include a full description of key principles of cancer causation and prevention that have become evident during the past 50 years. However, World Cancer Report recognizes the needs of readers for which at least some of the included topics are new. Therefore, each chapter includes information on the principles that are widely recognized as underpinning progress and the direction of research. This information, presented in the Fundamentals sidebar, enables readers to readily understand the context and relevance of the most recent research.
Accessible text – minimal use of abbreviations and jargon
World Cancer Report exemplifies a multidisciplinary approach to the geographical distribution, causation, biological determinants, and prevention of cancer, as well as the description of key data for 20 different cancer types, including blood cancers. Disciplines represented in particular chapters include epidemiology, cell and molecular biology, pathology, pharmacology, and behavioural science, together with communication, regulation, and public health. Including a comprehensive account of each discipline as background to the chapters would take World Cancer Report far beyond a manageable size. However, the text of each chapter has been rendered as accessible as possible to those not familiar with the relevant disciplines.
Use of abbreviations has been avoided where practicable, and every attempt has been made to avoid jargon specific to any particular discipline. Each chapter includes cross-references to other chapters that provide relevant background information or in which a particular issue is discussed in greater detail. Each chapter includes both a Summary of the content and a Fundamentals sidebar, which provides the context for advances in research. These measures will enable professional readers from many backgrounds to appreciate and benefit from information provided in the new World Cancer Report.
A high graphic content
A feature of World Cancer Report, since it was first published in 2003, is its high illustrative content. The new World Cancer Report includes hundreds of maps, charts, diagrams, and photographs. Maps show the geographical distribution of cancer occurrence. Charts typically indicate the relationship between two variables and increase confidence that any such relationship is not the outcome of chance. Diagrams are particularly useful to describe biological processes and show how an influence from the external environment is transmitted through molecular messengers such that a particular cellular response is evoked. Photographs typically place the information about cancer in context by illustrating the character of particular regions or environmental situations related to the prevalence of one or more tumour types. Overall, the high graphic content permits more immediate engagement with principles set out in the text and is likely to attract students seeking to understand key aspects of cancer causation and prevention.
Authors and reviewers from across the globe
Authors and reviewers who contributed to the new World Cancer Report were selected from experts worldwide who have contributed to the peer-reviewed medical and scientific literature. The authors of the chapters describing cancer in Africa, China, India, and so on are drawn from those particular countries or regions. The global burden of cancer was summarized by IARC researchers using data from the worldwide network of cancer registries, as published in full in the series Cancer Incidence in Five Continents. Because cancer research is an international enterprise, chapters describing the causes and development of malignancies reflect the global cancer research community. As a result, the title of World Cancer Report indicates not only the scope of the publication but also the extent of scientific participation in generating its content.
Comprehensive assessments are available for all aspects of oncology and cancer research. In addition to long individual research publications, review articles that include dozens of pages and cite hundreds of references ensure that those working in particular fields are aware of the details and subtle differences that have emerged from, in some cases, several hundred studies relevant to a particular topic.
World Cancer Report is not a compilation of comprehensive reviews. The authors were selected because their expertise affords the authority needed to present a concise overview of what is almost invariably a complex field of investigation. The number of references cited in each chapter has been extremely restricted. Thus, World Cancer Report offers to any cancer professional the opportunity to be reliably informed about parallel but relevant fields of investigation without undertaking a lengthy programme of reading.