The Epidemiology of Breast Cancer: An Up-to-Date Synopsis and Suggestions for the Future

Abstract

Breast Cancer Epidemiology provides a comprehensive, and the most up-to-date review of what is known about how, when and why breast cancer happens. The most interesting feature of this book is that it does not necessarily stop at what is firmly known, based on definitive controlled evidence, but it dares to provide a deep insight into what is likely and what might be, including scenarios (e.g., screening), which are still being developed and are yet to be fully understood.

Christopher I Li, (Division of Public Health Sciences, Fred Hutchinson Cancer Research Center and Department of Epidemiology, University of Washington, DC, USA) has organized this book in an interesting series of chapters, each dealing with one of the main topics of breast cancer epidemiology.

The book provides a punctual summary of our knowledge of breast cancer but, when looked at by a breast clinician with nonprofessional epidemiological skills, it has the unusual and very interesting feature of using existing epidemiological evidence to suggest reasonable preventive and clinical options, possibly challenging existing options.

As a first example, the book stresses the evidence based on the importance of physical activity and weight control, raising a real caveat for what is happening to developed countries where weight is increasing, healthy food is neglected and dietary habits are poor. At the same time a sterile message in favor of cancer prevention is widely diffused. In addition, attention is directed towards smoking and the fact that a third of cancers are determined by inappropriate diet is totally ignored.

“Few established breast cancer risk factors are modifiable. However, increasing physical activity and maintaining weight during a woman's adult years offer both individual and population-based opportunities for lowering women's risk of breast cancer”.

A second example is a realistic opinion regarding the reality of the relevance of inherited predisposition. While genetic aspects have largely colonized journals and congresses in recent times, and it looks like caring for identified patients at a high genetic risk is the most urgent priority in breast cancer prevention, this book reminds doctors that although a number of “gene mutations carry high increased risk … they are also quite rare and account for a negligible portion of breast cancer incidence”. In other words, caring for hereditary breast cancer may benefit a few but will not impact on the overall incidence and mortality figures. Moreover, the book also reminds readers that, when such genetic mutations are discovered, their “risk of breast cancer might be greatly reduced by prophylactic bilateral mastectomy or bilateral oophorectomy”, indeed a very aggressive approach, which, nevertheless, is rarely offered to women as it is the most unpleasant, but at the same time, the most rewarding preventive option.

A third example is the clear invitation to be cautious regarding the importance of breast radiological density. Density is a very fashionable topic and suggests that concentrating on women with dense breasts as a risk factor for developing the disease is a promising option. On the contrary, clear figures are provided demonstrating that “the available evidence is insufficient to conclude that the mammographic density can be used as a surrogate marker for breast cancer and further research to examine the potential role of mammographic density as a mediator of the effects of other risk factors is required”.

Finally, the book provides a very intelligent and evidence-based point of view on breast cancer screening, particularly as far as women aged between 40–49 years are concerned, this being one outstanding problem for health providers. Women aged between 40–49 years are currently excluded by active invitation in organized screening programmes and this is often criticized. The clear message to national health services is that in this age group screening is not highly cost effective, since saving one life requires ten-times more screening examinations as compared with women aged 50–69 years and the cost per life-year gained is five-times higher. The clear message to women is that the evidence of screening efficacy in reducing breast cancer mortality owing to early detection at age 40–49 years is not reassuring. In order to avoid false reassuring beliefs and benefit overestimates, a clear message should be thus conveyed to women aged 40–49 years that “the absolute benefit of screening mammography is small”.

Sample excerpt

Foreword by JR Daling (Fred Hutchinson Cancer Research Center, Seattle, Washington, DC, USA)

“Chapters focus on the roles of traditional etiologic risk factors, as well as more recently evaluated exposures, and, when evaluable, how risks vary by demographic factors (e.g., age, menopausal status and age ethnicity) and tumor characteristics (e.g., stage and hormone receptor status). The inclusion of chapters on screening, diagnosis and treatment, and survival make this the most up-to-date and comprehensive book on breast cancer available”.

Some reading impressions

Although the text is obviously full of data and figures relating to epidemiological evidence, it is written in a very fluid and simple style that is easy to understand for students and young doctors who may be less skilled at epidemiological and statistical jargon. This book is not intended only for specialists, but to all those who are involved in providing breast cancer care at any level. In addition, I would strongly advise its reading to all breast cancer researchers before going into a new study design: they might discover something they had ignored about breast cancer and be able to look at their research topic from a new, different and much more problematic point of view, possibly deciding that on the basis of what is known on breast cancer epidemiology, their research is no longer so important or that it should be aimed at a different target.