Tamoxifen

Once DCIS treatments are completed, tamoxifen is often recommended, even though this too is controversial.

Taking tamoxifen has its risks and side effects. According to the American Cancer Society, it increases the risk of endometrial (uterine) cancer and blood clots, although for uterine cancer, only by 1.6% in the tamoxifen group, compared with 0.5% in the placebo group (with an even lower risk of developing a serious blood clot). A 2009 study by Dr. Li also showed that women who used tamoxifen for five or more years were about four times more likely to develop a more aggressive ER-negative tumor in their other breast. Common side effects of tamoxifen are menopausal-like hot flashes, night sweats, and vaginal dryness.

An article entitled Tamoxifen: A Major Medical Mistake? discusses further the darker side of tamoxifen. In addition, here is a thorough list and review of 51 Abstracts with Tamoxifen Research.

According to Dr. Susan Love: “Tamoxifen is not a mandatory treatment. It is a choice. To decide whether it is right for you, you need to weigh the risks versus the benefits.” To do this, a study’s relative risk numbers must always be compared to its absolute risk numbers. For instance, when a 2005 study known as P-1 reported that tamoxifen reduced invasive breast cancer recurrence by 42%, the absolute risk reduction merely went from 4.25% to 2.48%, an actual reduction of only 1.77%.  Again in 1998, although the Breast Cancer Prevention Trial found that tamoxifen reduced the incidence of breast cancer in women with atypia by 86 percent, when broken down to absolute risk reduction, this number was less than 1%.

Please listen to this video clip by Dr. Pam Popper as she explains how the absolute and relative risk reduction statistics on tamoxifen can be presented in misleading ways.

Dr. Michael Lagios, an international DCIS expert and pathologist reports that the 2011 updates of two trials (NSABP-B24 and UK/ANZ) employing tamoxifen as an adjuvant agent in DCIS patients resulted in the following commentary by Warrick and Allred. They “conclude that tamoxifen is probably overused, and advocate more selective use. They particularly note that the major benefit would be seen in patients who are younger (pre-menopausal) with extensive high-grade disease and/or narrow margins, and clearly only those that are ER positive.”

On his website, Dr. Lagios states: “The clinical benefit of tamoxifen intervention based on the randomized trials is meager at best. There appears to be no benefit, at least in the UK/ANZ trial for tamoxifen among irradiated patients, and the benefits when claimed are very small.”

Taking tamoxifen is a personal choice. Evaluating its benefit should always be based on the study’s absolute risk reduction, not the relative risk reduction. Once known, you can then decide if the benefits outweigh the risks for you.

A common question is, “Are there natural alternatives to Tamoxifen?” Please see Elyn Jacob’s article on this topic as well as:

Natural Alternatives to Aromatase Inhibitors 

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2 thoughts on “Tamoxifen”

  1. Does this research apply to pre-surgical use of Tamoxifen? I’m considering tamoxifen + increased surveillance in lieu of the recommended mastectomy for 5cm, grade 3 er+/pr+ DCIS. Oncologist said tamoxifen could be used only for 5 years anyway, so it feels like I’m delaying a decision. I’ve reached out to Dr. Lynch (who recommended your site!) and am not a candidate for COMET. Thanks for all the info, Donna.

    • Hi Laura,
      Some research is after excision (NSABP-B24 and UK/ANZ) and some is before (Breast Cancer Prevention Trial ).

      Did you see my post from my visit with Dr. Laura Esserman in 2012? https://dcis411.com/2012/02/09/dr-esserman-touts-tamoxifen/

      Based on all the information I read, I personally never considered taking tamoxifen.

      Be sure to read all the studies carefully and also all the links describing the alternatives to tamoxifen.

      There are Facebook groups for both alternatives and if you choose to take it. There is no rush to making decisions with DCIS. Take your time and come to the conclusion that feels right to you!

      Please let me know if you have more questions or need any guidance.

      Blessings to you,
      Donna

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