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Susan R. Davis, Rory Wolfe, Helen Farrugia, Angeline Ferdinand, Robin J. Bell, Author Response, The Journal of Sexual Medicine, Volume 7, Issue 2_Part_2, February 2010, Pages 1036–1037, https://doi.org/10.1111/j.1743-6109.2009.01563_1.x
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We acknowledge that determining whether exogenous testosterone exposure influences breast cancer risk presents a challenge as confounding of this issue is problematic. Confounding by exposure to exogenous estrogen therapy (ET) or estrogen plus progestin therapy (EPT) is one aspect. Previous researchers who have attempted to address this have reported that the addition of exogenous testosterone to ET, or EPT does not result in any additional increase in breast cancer risk, but rather, the risk reflects that of the concurrent ET or EPT [1]. In relation to this issue of confounding by exogenous use of E and/or P, our study included both premenopausal and postmenopausal women treated with testosterone [2]. The women who were premenopausal at the time of testosterone exposure were not concurrent ET/EPT users although most, but not all, postmenopausal women were concurrent users. Hence the statement in the letter that “the majority of women in the cohort exposed to testosterone were also exposed to estrogen” is not correct. We considered an internal comparison of postmenopausal ET/EPT users versus non users. However this was an impossible task, as we have highlighted, because in the years of follow up some women ceased ET/EPT therapy, some commenced therapy (including women premenopausal at exposure who had since become postmenopausal) and some underwent hysterectomy and /or oophorectomy and changed from EPT to ET such that the risk conferred by systemic hormone therapy varied over time. Nonetheless, that all cases of breast cancer we observed were in older women who had used systemic hormone therapy, with only one woman being a current testosterone user at diagnosis, is consistent with the findings of Jick et al. [1,3].
