I have always known that dense breast tissue is much more difficult to read on a mammogram than more fatty tissue, but did not know that this characteristic might be enhanced by taking estrogen supplements. Knowing this, it makes sense that anything that reduces estrogen, such as tamoxifen, might reduce breast density and perhaps reduce the risk of breast cancer.
However, unless the risk of getting breast cancer is extremely high, I do not feel the risks of taking tamoxifen or other estrogen-reducing drugs, is a safe prevention method, although avoiding supplemental estrogen is obviously a good idea.
Hopefully, a good method of reporting breast density will be developed and those with very dense breast tissue will be able to be checked with MRI. I have a friend with dense breasts whose extensive cancer did not show up on mammograms until after it had become visible to the naked eye, and even then showed only as a couple of shadows even though there were five large tumors. An MRI revealed all five with clarity.
“Objectives-Evaluate known breast cancer risk factors in relation to breast density…
Results-Initial analyses showed a strong inverse influence of age and body mass index (BMI) on breast density. In addition, women with late age at menarche, late age at first birth, premenopausal women, and those currently using hormone therapy (HT) tended to have higher breast density, while those with greater parity tended to have less dense breasts.
Analyses stratified by age and BMI suggested interactions, which were formally assessed in a multivariable model. The impact of current HT use, relative to nonuse, differed across age groups, with an inverse association in younger women, and a positive association in older women (p < 0.0001 for the interaction).
The positive effects of age at menarche and age at first birth and the inverse influence of parity were less apparent in women with low BMI than in those with high BMI (p = 0.04, p < 0.0001 and p = 0.01, respectively, for the interactions). We also noted stronger positive effects for age at first birth in postmenopausal women (p = 0.004 for the interaction). The multivariable model indicated a slightly positive influence of family history of breast cancer.
Conclusions-The influence of age at menarche and reproductive factors on breast density is less evident in women with high BMI. Density is reduced in young women using HT but increased in HT users of age 50 or more.