I had taken oral estrogen for years after a complete hysterectomy in 1987. After lumpectomy and radiation for a very small non-invasive breast cancer in 2013, I refused letrozol and went to see Dr. Stephen Swanson in Lincoln, NE whom I knew, from a talk he had give after the results of the big study of post-menopausal estrogen, to be a strong advocate. I was having acute estrogen withdrawal symptoms.
He told me he did not believe estrogen caused breast cancer, but that the compounded estrogens given as oral estrogen replacement therapy, were the culprits instead. Since oral estrogen passes through the digestive tract, it generates numerous metabolites, none of which have, or will be, tested individually.
He prescribed pure estradiol applied as a patch and a compounded estradiol suppository, also of pure estradiol, which was less messy, better distributed, and less expensive by far than commercial estradiol cream.
I have been using both, since 2013, have greatly benefited in both health and comfort, and, knock on wood for continuance, remained cancer free.