Does tamoxifen have a place in TNBC treatment? The answer is still "no."

Women with the BRCA 1 or 2 mutations may benefit from the use of tamoxifen, even if they are estrogen negative, but the evidence so far is not convincing.  According to research in the Journal of Clinical Oncology, use of tamoxifen reduced the risk of cancer in the opposite breast by more than half among both BRCA1 and BRCA2 mutation carriers no matter what the receptor status was of the original tumor.

The study looked at information on 1,583 BRCA1 and 881 BRCA2 mutation carriers who took tamoxifen after their breast cancer diagnosis;  of these 24 percent of the BRCA 1 took tamoxifen and 52 percent on the BRCA 2 carriers took tamoxifen.   

This is an intriguing study and I would not make much of it until or unless a clinical study is started to look at the issue more closely in a more controlled environment. The numbers of women on tamoxifen were small in the research, because tamoxifen has not been recommended for TNBC and many cases of cancer among those with the BRCA mutations are TNBC. Also, we're not sure how other variables were controlled, or if they were, so those could play a part. So I would not start thinking tamoxifen is a benefit to TNBC—there's way too many questions right now, and the side effects of tamoxifen are significant. The general recommendation is not to use tamoxifen for TNBC, and that recommendation still stands.

• Read more about TNBC in my book, Surviving Triple-Negative Breast Cancer.

• Please consider a donation to Positives About Negative to keep this site going.  This work is entirely supported by readers.  Just click on the Donate button in the right of the page.  Thank you!

Can Tamoxifen Help Hormone-Receptor-Negative Breast Cancer?

Neither Tamoxifen nor Arimidex are recommended for hormone-negative cancer. Breast cancer research, especially from the Early Breast Cancer Trialists’ Collaborative Group (EBCTCG), demonstrates that these drugs do not help hormone-receptor-negative cancer. The Arimidex Web site specifically notes that the drug is for women with estrogen-positive breast cancer.

The situation gets a little muddy in terms of weakly positive tumors, which was true in my case—I was weakly positive for progesterone. These tumors are considered a mixture of positive and negative and, therefore, might react to the anti-estrogen drug Tamoxifen or an aromatase inhibitor like Arimidex. Wendy Chen, MD, of Dana Farber Cancer Institute and Brigham and Women's Hospital and a participant in the Nurses Health Study (NHS) research, says the NHS studies classify a tumor as hormone positive if it is even borderline positive. So those of us with mixed readings, in that case, would have been included in the data for estrogen-positive patients.

Still, she says, “The cut-off for ER positivity can vary from lab to lab and study to study.” Because of this, she says, “there is no one right answer” to the question of whether Tamoxifen or Arimidex might help women with weakly positive tumors."

The California Teachers Study (CTS) , published in the Archives of Internal Medicine , has another take on this.

According to the CTS, even though tumors of hormone-negative cancer do not need estrogen to grow, at the stem-cell stage they may be initially formed because of out-of-kilter hormones that are linked to insulin. So, while estrogen is not the perpetrator, it may be an accessory to the crime, aiding insulin in the initial formation of the disease.

Tamoxifen, then, could be of some benefit, says Leslie Bernstein, PhD, professor and dean for faculty development at the City of Hope National Medical Center. Bernstein, who was a researcher on the CTS study, says that Tamoxifen “suppresses the insulin-like growth factor. Its effects could work with ER-negative cancer.”

Data from the Early Breast Cancer Trialists’ Collaborative Group (EBCTCG), show the overall recurrence rate after five years for women on Tamoxifen as 3.2 percent a year. For women who had not taken Tamoxifen, it was 4.5 percent a year. This is an average, of course, so half of the women in the study had higher recurrence rates, half had lower. Does this mean that women with mixed or weak readings would benefit less than average? That sort of information may be embedded in research, but I have yet to dig it out. I’ll keep trying.

Again, we get back to the fact that cancer is as unique as our DNA, so one woman’s breast cancer is not the same as another’s, and the decisions on treatment have to be made based on her specific circumstances.