December 2005

Over the past several years there has been much Internet speculation and media attention regarding a possible link between antiperspirant use and breast cancer. Research studies, however, have resulted in contradictory and non-conclusive findings thus far. The evidence for such an association existing has not been established, and NBCCF believes further research is warranted before such a claim can be made.

Research Evidence
Few studies have directly examined the relationship between antiperspirant use and breast cancer. And while one study's findings suggest antiperspirant use does increase breast cancer risk, another study found no evidence to support such an association.

In 2002, researchers in Washington State conducted an observational, case-control study¹ involving 813 women with breast cancer and 793 women without breast cancer and interviewed all women about their personal hygiene habits, such as the use of products applied for underarm perspiration.² The study found that the risk for breast cancer did not increase with antiperspirant or deodorant use, with antiperspirant or deodorant use among women who shaved with a blade razor, or with application of antiperspirant or deodorant within one hour of shaving. The study's findings did not support the hypothesis that antiperspirant use increases breast cancer risk.

In 2004, researchers in Chicago surveyed 437 women diagnosed with breast cancer on the frequency of their prior antiperspirant or deodorant use and underarm shaving habits.³ The researchers found that both a higher frequency and an earlier starting age of antiperspirant or deodorant use with underarm shaving were associated with an earlier age of breast cancer diagnosis. The author concluded that while these factors might play a role in breast cancer, the extent to which antiperspirant use, deodorant use, and underarm shaving might be involved in an earlier breast cancer diagnosis was not clear. This study's retrospective cohort design is also vulnerable to recall bias. Additionally, this study did not include an appropriate control group. The findings were all based on women with breast cancer, with no comparison made to women not diagnosed with breast cancer.

Several laboratory studies conducted by Darbre, et al. examined potential biologic pathways through which antiperspirants could affect breast cancer risk. One such study examined the presence of parabens in human breast tumors.⁴ Parabens are a class of chemicals shown to mimic estrogen, and commonly added to antiperspirants, deodorants, and other cosmetics as a preservative. This study examined 20 different human breast tumors for the presence of parabens, and found traces in all samples. The findings of this study indicate that this chemical can be found intact in the human breast. The study design, however, did not include an appropriate control. The findings cannot be interpreted to indicate any association between application of antiperspirant or deodorant and breast cancer because no comparison was made to healthy breast tissue. A more recent study by Darbre examined potential biologic pathways through which aluminum salts, the active ingredient in antiperspirants, could affect breast cancer risk.⁵ This study found that aluminum salts, in the form of aluminum chloride and aluminum chlorhydrate, have the potential to interfere with estrogen receptor functioning through the inhibition of estrogen binding to its receptor, and through increased expression of an estrogen-regulated reporter gene. The author noted that the mechanism of binding inhibition remains to be determined and the potential effects of aluminum salts on endogenous estrogen-regulated genes still need to be investigated. These laboratory findings should be viewed as preliminary investigations into possible mechanisms through which underarm topical application of a chemical could be associated with breast cancer. These studies merely address biologic plausibility, and in no way establish that antiperspirants cause breast cancer.

Conclusion
NBCCF believes that in addition to the scarcity of studies examining the association between antiperspirant use and breast cancer risk, the evidence accumulated so far has been contradictory and inconclusive. These previous studies all have design limitations, and have not been able to identify a true association between antiperspirant use and breast cancer. Until further studies are conducted that add significantly to the literature, NBCCF believes that the published research does not constitute enough evidence to conclude that there is a relationship between antiperspirant use and breast cancer.

Even well designed and conducted observational studies yield results that are hypothesis-generating, warranting further study for closer examination of a potential relationship between an exposure and breast cancer risk. Laboratory studies complement epidemiological studies by investigating the mechanisms of interaction between an exposure and the breast cell. Both laboratory and epidemiological studies need to include appropriate controls to determine whether the effect of the investigated exposure is truly specific to cancer. In this case, the case-control study did not conclude there was an association between antiperspirant use and breast cancer, the cohort study had methodological flaws because it lacked a control group, and the laboratory studies are still in the early stages.

NBCCF supports legislation establishing breast cancer and environmental research centers to carry out a national strategy for understanding the links that may exist between the environment and breast cancer. The Breast Cancer and Environmental Research Act (see NBCCF's Legislative Priority to Enact the Breast Cancer and Environmental Research Act) would facilitate research on environmental exposures, such as chemicals in antiperspirants, potentially related to the development of breast cancer.⁶

The U.S. Food and Drug Administration along with the National Cancer Institute and other research and advocacy organizations recently reiterated that "no existing scientific or medical evidence links the use of underarm antiperspirants or deodorants to the subsequent development of breast cancer."⁷ NBCCF agrees with this statement.

About NBCCF
The National Breast Cancer Coalition Fund is a grassroots organization dedicated to ending breast cancer through the power of action and advocacy. The Coalition's main goals are to increase federal funding for breast cancer research and collaborate with the scientific community to implement new models of research; improve access to high quality health care and breast cancer clinical trials for all women; and expand the influence of breast cancer advocates in all aspects of the breast cancer decision making process.

Footnote

¹A case-control study starts with the identification of persons with the disease ("cases") of interest and a suitable comparison or reference group of persons without the disease ("controls"). The relationship of an attribute to the disease is examined by comparing the diseased ("cases") and non-diseased ("controls") with regard to how frequently an attribute is present or the levels of the attribute in each of the groups. Such a study can be called "retrospective" because it starts after the onset of disease and looks back to postulated causal factors. Cases and controls in a case-control study may be accumulated "prospectively"; that is, as each new case is diagnosed, she is entered in the study. Nevertheless, such a study may still be called "retrospective" because it looks back from the outcome to its causes.

Even when well designed and conducted, case-control studies in general are subject to recall bias. Usually recall bias causes the association between a potential factor and a particular disease to appear stronger than it actually is because cases tend to more frequently remember previous exposures than controls.

²Mirick DK, Davis S, Thomas DB. Antiperspirant use and the risk of breast cancer. Journal of the National Cancer Institute 2002; 94(20): 1578-1580.

³McGrath KG. An earlier age of breast cancer diagnosis related to more frequent use of antiperspirants/deodorants and underarm shaving. European Journal of Cancer Prevention 2003; 12(6): 479-485.

⁴Darbre PD, Aljarrah A, Miller WR, Coldham NG, Sauer MJ, Pope GS. Concentrations of parabens in human breast tumours. Journal of Applied Toxicology 2004; 24(1): 5-13.

⁵Darbre PD. Aluminum, antiperspirants and breast cancer. Journal of Inorganic Biochemistry 2005; 99: 1912-1919.

⁶One of NBCCF's legislative priorities for 2005 was to support the enactment of the Breast Cancer and Environmental Research Act. In 2002, NBCC testified before the Senate Health, Education, Labor and Pensions Subcommittee on Public Health in support of the Breast Cancer and Environmental Research Act

⁷U.S. Food and Drug Administration. Antiperspirant awareness: it's mostly no sweat. FDA Consumer magazine. July-August 2005.