Updated Guidelines for Adjuvant Tamoxifen in Hormone-Positive Breast Cancer

Posted on May 29th, 2014 by

The American Society of Clinical Oncology (ASCO) has updated their guidelines for the use of adjuvant endocrine therapy, particularly adjuvant tamoxifen (Nolvadex®), for women with hormone receptor-positive breast cancer. This update, which focuses on duration of treatment, was published early online in the Journal of Clinical Oncology.

A majority of breast cancers are estrogen receptor-positive (ER-positive), or hormone-positive, meaning they are stimulated to grow by the female hormone estrogen. Depriving ER-positive breast cancers of estrogen can slow their growth. Tamoxifen is an anti-estrogen that has long been a mainstay of hormonal (or endocrine) therapy for breast cancer.

Adjuvant therapy is treatment given after primary treatment to lower the risk that cancer will come back. Five years of adjuvant tamoxifen has been shown to reduce the risk of recurrence and death from ER-positive breast cancer, making this approach and duration the standard treatment for quite some time; however, researchers have been evaluating whether longer treatment with tamoxifen is even more effective.

To update the guidelines on the use of adjuvant endocrine therapy in hormone positive breast cancer, an ASCO Update Committee reviewed findings from randomized clinical trials (where participants are assigned by chance to treatment groups) conducted between 2009 and 2013 as well as three trials using selected medical records (historical trials). In particular, they looked at survival, disease recurrence, and adverse events in the trials they reviewed.

In the course of the review, the Update Committee found evidence to suggest that extending the duration of tamoxifen treatment beyond the five-year standard could improve breast cancer survival. Specifically, women in two large studies who used tamoxifen for a total of 10 years experienced “modest gains in survival” compared with those who used tamoxifen for five years. As well, women treated for 10 years had a lower risk of recurrence and of developing cancer in the other (previously unaffected) breast.

Based on these findings, ASCO has updated their guidelines on the use of adjuvant tamoxifen for women with hormone receptor-positive breast cancer: they’ve extended the recommended duration of treatment to 10 years from the previous five years. In the update ASCO recommends that pre- and perimenopausal women are offered 10 years of tamoxifen and that postmenopausal women are offered either 10 years of tamoxifen or five years of tamoxifen followed by five years of an aromatase inhibitor (a type of hormonal therapy for postmenopausal women).

As always, patients are encouraged to discuss all treatment options with their physician in order to make the best decision for optimal care.


Burstein HJ, Temin S, Anderson H, et al. Adjuvant Endocrine Therapy for Women With Hormone Receptor–Positive Breast Cancer: American Society of Clinical Oncology Clinical Practice Guideline Focused Update. Journal of Clinical Oncology [early online publication]. May 27, 2014.

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Tags: Breast Cancer, Carcinoma In Situ Breast cancer, News, Stage I Node Negative Breast Cancer, Stages II-III Breast Cancer, tamoxifen, treatment duration, Uncategorized

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