Tobacco Industry Influence on Breast Cancer Research

Through a study recently published in Tobacco Control[1], a team of researchers from the University of California, San Francisco (UCSF) examined the tobacco industry's strategies to influence scientific research, public policy, and public opinion surrounding the link between smoking and breast cancer. Drawing on an analysis of thousands of internal industry documents made available following a court ruling and accessible through the Truth Tobacco Industry Documents Library, the authors shed light on the industry's efforts to divert attention from tobacco's potential role in the genesis of breast cancer.

The study is based on an innovative method called "situational scoping," combining academic expertise and civil society involvement. The researchers explored 19,719 documents from the archives of the Council for Tobacco Research (CTR) and the Tobacco Institute (TI), covering the period from the 1950s to 1998. Of these documents, 28 % were scientific publications, 19 % concerned ongoing research projects, and 6 % concerned internal communications. This approach made it possible to identify and map the industry's strategic responses to nine events deemed to be threats or opportunities for their commercial interests.

Breast cancer: a major public health issue

Breast cancer is one of the most common cancers in women today. Despite growing recognition of the role of environmental factors, the effects of active and passive smoking on breast cancer incidence have long remained underestimated. However, recent meta-analyses confirm an increased risk of breast cancer linked to tobacco exposure, whether active or passive. Thus, according to some studies, the relative risk of breast cancer could be increased by 10 to 30 times in women exposed to passive smoking.

Link between smoking and breast cancer deliberately contested

The internal documents analyzed show that, as early as the 1980s, the Tobacco Institute (TI) and the Council for Tobacco Research (CTR) perceived studies suggesting an association between secondhand smoke and breast cancer as threats to their commercial interests. Faced with these results, they implemented a structured response strategy aimed at delegitimizing scientific work pointing to this association. For example, they systematically criticized the methodology of studies by researchers such as Hirayama (Japan), Morabia, and Wells (United States), whose work indicated an increased risk of breast cancer linked to exposure to tobacco smoke. To this end, the industry relied on its own biostatisticians, such as Marvin Kastenbaum, or experts financially linked to its activities, such as Nathan Mantel, to produce counter-analyses and sow doubt in scientific and media circles.

At the same time, the CTR funded a vast body of research into other causes of breast cancer, such as genetic, hormonal, and dietary factors, with the explicit aim of diverting attention from the risks associated with tobacco. The study identifies at least 48 projects funded by the CTR in this regard, including 32 on genetic causes, 9 on hormonal and dietary causes, and several studies promoting the erroneous idea of a protective effect of tobacco through estrogen suppression. Some publications claimed that women who smoke had a lower risk of breast cancer than non-smokers—a hypothesis since refuted by numerous independent studies.

A systemic and persistent scientific influence strategy

The analysis highlights a coherent, coordinated, and long-term strategy by tobacco industry players to prevent the existence of a scientific consensus around the health risks of their products. This strategy was not limited to funding favorable research: it also included organizing biased symposia, distributing biased newsletters, highlighting fringe publications, and selectively exploiting statements by respected scientists (often taken out of context) to artificially support industry positions.

The Tobacco Institute has gone so far as to claim that the increase in lung cancer cases among non-smoking women may actually result from metastasis of misdiagnosed breast cancers, a move aimed at challenging studies attributing this mortality to secondhand smoke. These pseudoscientific arguments have been relayed in publications, conferences, and internal documents aimed at policymakers and health professionals.

These tactics are part of a broader, well-documented strategy by which the tobacco industry seeks to minimize, relativize, or deny the health risks associated with the use of any of its products (cigarettes, heated tobacco, vaping). By presenting itself as a "neutral" or "responsible" scientific actor, the industry attempts to preserve its legitimacy and influence, while hindering the adoption of evidence-based public health policies.

©Generation Without Tobacco

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[1] Han E, Crosbie E, Ling P, et al Tobacco industry influence on breast cancer research, policy and public opinion: scoping the Truth Tobacco Industry Documents Tobacco Control Published Online First: 23 April 2025. doi: 10.1136/tc-2024-05872