Tamoxifen is a selective estrogen receptor modulator that is currently being used to prevent a recurrence of estrogen receptor positive and progesterone receptor positive breast cancers.
From http://en.wikipedia.org/wiki/File:Tamoxifen_Structural_Formulae.pngTo do this, tamoxifen mimics the structure of estrogen and binds to the estrogen receptor, preventing the estrogen dependent pathway that induced the cancer to begin with. There are many adverse side effects to this drug such as an increased risk of blood clots and an increased risk of uterine cancer.
This raises into question, how effective is tamoxifen at preventing breast cancer recurrence (and in some women preventing breast cancer in and of itself)? Do the risks, such as uterine cancer, outweigh the benefits?
Should tamoxifen be used to prevent progesterone receptor positive breast cancers? Tamoxifen is specific to estrogen receptor positive breast cancers. Although progesterone is similar in structure to estrogen, it is likely that the binding site of the progesterone receptor is different from the binding site of the estrogen receptor. Is tamoxifen, then, even effective for prevention of progesterone receptor positive breast cancer?
To explore this, an interesting study looks at tamoxifen in the prevention of estrogen receptor negative and progesterone receptor positive breast cancer. Most of these cases are premenopausal with little option for prevention besides tamoxifen. According to the study, tamoxifen may be less effective in this type of breast cancer. Why, then, is tamoxifen being used for prevention in all hormone receptor breast cancers if the benefit is much less for progesterone receptor positive breast cancers (especially given the risks of taking tamoxifen)?
