Image: Mobile phones are one of a number of potential carcinogens that have been recently reviewed by the IARC. Credit: Robin Worrall
It is nearly 100 years since scientists at The Institute of Cancer Research in London made a groundbreaking discovery by identifying the cancer-causing chemicals in cigarette smoke. The discovery of polycyclic aromatic hydrocarbons was pivotal in understanding the link between smoking and cancer, significantly advancing cancer research and public health awareness.
Since then, the World Health Organisation’s International Agency for Research on Cancer (IARC) has evaluated more than 1,000 agents. More than 500 have been identified as either carcinogenic, or possibly carcinogenic, including diesel exhaust fumes, and hormone replacement therapy. Most recently, perfluorooctanoic acid (PFOA), one of a group of so-called ‘forever chemicals’ which can stick around in the environment long after people have finished with them, was found to be carcinogenic.
These findings are published by the IARC in detailed reports called ‘monographs’ which help scientists, health professionals, and policymakers understand and manage cancer risks.
Classic texts for epidemiologists
In 1980, the IARC published two classic books called Statistical Methods in Cancer Research, edited by Dr Norman Breslow and Dr Nicholas Day. Affectionately known in the field as “Breslow and Day”, these seminal works were instrumental in the training and education of several generations of epidemiologists, providing essential research methodologies for the study of cancer and other chronic diseases.
Studies carried out using the methods outlined by Breslow and Day have formed the basis of much of our understanding about the preventable causes of cancer in humans, as evidenced in the evaluations carried out by the IARC Monographs programme.
However, as with any scientific field, advancements and new methodologies meant that an updated version of the books was needed to ensure accuracy and continued relevance.
Bias, for instance, can lead to incorrect conclusions about the relationship between exposures and outcomes. For example, if a study incorrectly measures the amount of a harmful chemical that people are exposed to, it might wrongly conclude that the substance is safe.
Planning the new book
Plans for a new version of the book were hatched more than five years ago during one of my regular visits to Lyon, France, to work with Dr Mary Schubauer-Berigan who leads the IARC monographs Programme.
It was a huge undertaking, but we were fortunate that we didn’t have to do it alone. We were accompanied by a team of 35 scientists from around the world, and our colleague Professor David Richardson from the University of California, Irvine Program in Public Health who was on sabbatical at IARC.
Our goal for this new book was to summarise these methods and, in keeping with the spirit of those original volumes, to present them in a way that is accessible to epidemiologists and other research workers and statisticians without extensive epidemiological training.
In 2022, we held an intensive workshop in Lyon to debate the ideas and to hash out the examples. Mobile phones, red meat consumption, night shift work and opium consumption were all chosen as examples of potential carcinogens that have recently been reviewed by IARC and illustrate the wide range of challenges in epidemiological studies.
It is immensely gratifying to produce a book that encompasses the major developments in the field and to see your vision gradually take form.
After extensive editing and reviewing, the finished product, with its vibrant cover based on a painting by the French artist Robert Delaunay, has finally been published. We hope that it lives up to the spirit and scope of the original “Breslow and Day” and serves as a useful resource for generations of epidemiologists to come.
Thanks to funding by IARC and National Cancer Institute, Statistical Methods in Cancer Research Volume V: Bias Assessment in Case-Control and Cohort Studies for Hazard Identification is free to download. But for those who still think that ‘books furnish a room’, physical copies can be ordered in 2025.
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