Important Information about a recent Study on Breast Cancer Reduction

The latest on HRT and Breast Cancer Reduction from Dr Steven R. Goldstein, a Menopause Specialist in NYC. 

You would have to be living under a rock not to realize that there has been an explosion in interest in the menopausal transition. The membership in the Menopause Society (previously known as NAMS: North American Menopause Society) in two years has gone from 2,000 to 7,600. There is a tremendous amount of information on the internet and social media which, fortunately, has raised awareness about this time in women’s lives, but unfortunately, it is often with cherry-picked misinformation, and often by influencers who are “selling something” whether it be supplements, books, subscriptions, mailing lists, etc.

I wrote a lay-person book on perimenopause twenty-eight years ago called “Could It Be Perimenopause,” as well as the first medical textbook, “Perimenopausal Gynecology,” twenty-four years ago. Any of you in this transition now, or previously, are well aware of my interest and expertise in this arena.

I write to you today because of some exciting initial research that was presented at the American Society of Clinical Oncology last week. I have spoken to so many of you for such a long period of time about important nuances in hormone therapy. As I have often stated, I have a slide that says, “there is no such thing as estrogen.” My next slide in that lecture says, “What???” The next slide says, “THERE IS NO SUCH THING AS ESTROGEN!” The next slide says, “There are estrogens.”

Premarin, the estrogen that comes from pregnant horses’ urine, contains estradiol, a natural estrogen made by your ovaries when you are premenopausal, but also contains a number of other constituents, some of which have some SERM-like properties. SERM stands for selective estrogen receptor modulator, and drugs like tamoxifen and Evista (raloxifene) are SERMs. These are drugs that are estrogenic in some tissues (like bone) but anti-estrogen in other tissues (like breast). In fact, these are approved for breast cancer prevention. In that famous Women’s Health Initiative (WHI) study, stopped in 2002, women who did not have a uterus and took Premarin by itself, when followed over twenty years, had less breast cancer and less breast cancer death than those who took a placebo. In other words, Premarin has some SERM-like properties of its own. Estradiol does not. They are not the same. However, when mixed with any form of progestogen (the umbrella term for progesterone) there is a small but real increase in breast cancer regardless of which estrogen is employed.

A formulation available now for more than a decade, known as Duavee, combines this specific estrogen, Premarin, with yet another SERM drug called bazedoxifene. Premarin has been shown to reduce breast cancer risk and death in a double-blind, randomized study followed out over twenty years. All the SERMs, including bazedoxifene, are anti-estrogen in breast. I have seen data previously not published when a breast tumor was placed in an experimental animal and it was given tamoxifen, the tumor shrunk. Similarly, Evista (raloxifene) caused such a breast tumor to shrink. When given Duavee, the breast tumor also shrunk.

Pfizer did not do a breast cancer prevention trial with Duavee in 2013 because of the lack of ROI (return on investment). It would have been a five-year study of 40,000 women at a cost of two billion dollars and another year and a half to get it into the label. At that time, menopause was a relatively dirty word. If I went to a cocktail party and told women I was president of the Menopause Society, it cleared the room. Now in 2025, it is big news and big business.

The pilot study which was presented at the American Society of Clinical Oncology was conducted at Northwestern University by Dr. Kulkarni. They studied Duavee versus placebo in postmenopausal women who had DCIS (ductal carcinoma in situ, often erroneously referred to as Stage 0 breast cancer). They were specifically interested in a marker of cell growth and proliferation known as Ki67 in women with estrogen receptor positive precancers (DCIS).

Women with a biopsy showing DCIS received either placebo or Duavee for twenty-eight days and then had surgical excision of their mass. There was a statistically significant reduction in Ki67 in the breast tissue of those treated with Duavee compared to placebo, suggesting a potential protective effect. But equally important, women taking Duavee had an improvement in their hot flashes, and thus quality of life unlike women who often go on tamoxifen or raloxifene with mild to moderate potential for untoward side effects, mainly hot flashes, night sweats, and leg cramps.

Thus, this is one of the first published corroborations of what I have been telling patients for several years based on the science behind these molecules. Since both components of Duavee are proven anti-estrogens in breast, this finding is totally expected, but such study is, in fact, welcomed and necessary.

I hope this is of value to you personally. If not, feel free to share it with friends or family members who may be in this stage of their lives.

Dr Goldstein’s office is conveniently located on the East Side of Manhattan. If you are menopausal and struggling with the symptoms of Menopause, see Dr Steven R. Goldstein a leading Hormone Specialist in NYC.