Tamoxifen for 10 Years an Option: ASCO Guideline Update

Megan Brooks

May 27, 2014

Women with stage I to III hormone receptor–positive breast cancer should consider taking tamoxifen for 10 years, the American Society of Clinical Oncology (ASCO) says in a clinical practice guideline focused update.

"This update was prompted by emerging data demonstrating that longer durations of tamoxifen ― up to 10 years ― are more effective than shorter durations at preventing cancer recurrence and improving breast cancer survival," Harold J. Burstein, MD, PhD, co-chair of ASCO's expert panel that wrote the guideline update, told Medscape Medical News.

"Clinicians should consider longer durations of adjuvant endocrine therapy, up to a total of 10 years, for many patients," advised Dr. Burstein, breast oncologist at the Susan F. Smith Center for Women's Cancers at Dana-Farber Cancer Institute in Boston, Massachusetts.

The option of 10 years of tamoxifen therapy is recommended for both premenopausal women and postmenopausal women, although the latter also have the option of taking a sequence of tamoxifen and aromatase inhibitor therapy, Dr Burstein commented. Aromatase inhibitors are not recommended for premenopausal women.

Another co-chair of the expert panel, Jennifer Griggs, MD, MPH, from the University of Michigan in Ann Arbor, emphasized that it was important for clinicians and patients to discuss the trade- offs between potential risks for side effects and potential benefits of taking adjuvant endocrine therapy for up to 10 years.

"As with many decisions in breast cancer, the decision about extending adjuvant therapy is a shared one in which informational support is critical," she told Medscape Medical News.

The guideline, Adjuvant Endocrine Therapy for Women with Hormone Receptor–Positive Breast Cancer: American Society of Clinical Oncology Clinical Practice Guideline Focused Update, was published online in the Journal of Clinical Oncology on May 27. It replaces ASCO's 2010 guideline update.

Dr. Harold Burstein

Hormone receptor–positive breast cancer is the most common type of breast cancer; about 60% to 75% of women with breast cancer have estrogen receptor–positive breast cancer, and 65% of these cancers are also progesterone receptor–positive. "Adjuvant endocrine therapy is highly effective and appropriate for nearly all women with ER- and/or PgR-positive tumors," the guideline says.

To update the clinical practice guideline, the ASCO panel reviewed randomized clinical trials from January 2009 to June 2013. Two randomized trials on extended tamoxifen treatment ― one known as ATLAS (Lancet. 2013;381:805-816) and the other called aTTom (J Clin Oncol. 2013;31:6s; supplement, abstract 5) ― provided evidence for the new recommendation. There has been no new evidence on extended durations of aromatase inhibitors since the previous guideline update, the panel notes.

Key recommendations in the update are as follows:

  • Women diagnosed with hormone receptor–positive breast cancer who are pre-/perimenopausal should be offered adjuvant endocrine therapy with tamoxifen for 5 years, after which they should receive additional therapy based on menopausal status. If premenopausal, they should be offered continued tamoxifen for a total duration of 10 years. If postmenopausal, they should be offered continued tamoxifen for a total duration of 10 years or an aromatase inhibitor (AI) for a total duration of up to 10 years of adjuvant endocrine therapy.

  • Women diagnosed with hormone receptor–positive breast cancer who are postmenopausal should be offered adjuvant endocrine therapy with one of the following options: tamoxifen for 10 years; an AI for 5 years; tamoxifen for 5 years, then switching to an AI for up to 5 years; or tamoxifen for 2-3 years, then switching to an AI for up to 5 years.

  • Women who are postmenopausal and are intolerant of either tamoxifen or an AI should be offered the alternative type of adjuvant endocrine therapy. If women have received an AI but discontinued treatment at less than 5 years, they may be offered tamoxifen for a total of 5 years. If women have received tamoxifen for 2-3 years, they should be offered an AI for up to 5 years, for a total duration of up to 7-8 years of adjuvant endocrine therapy.

The guideline discusses issues clinicians face in communicating with women about taking adjuvant endocrine therapy for extended periods.

"Many of my patients are aware of the data supporting the benefit of staying on tamoxifen for longer than 5 years and are motivated to do anything they can to reduce their risk of recurrence," Dr. Griggs said. "Other women, particularly those who have experienced moderate to severe side effects for 5 years, are eager to discontinue tamoxifen."

For a woman with a higher risk for breast cancer (for example, positive lymph nodes or other factors that warranted chemotherapy), "I've been negotiating with them and offering a strategy where we revisit the ongoing use of tamoxifen one year at a time. This seems to be more acceptable that committing to 5 more years all at one time,” Dr. Griggs told Medscape Medical News.

"Other women have decided to come off tamoxifen after 5 years to see if the side effects they have had are truly due to tamoxifen. If the side effects they think are related to tamoxifen do not go away, they've told me that they'll go back on tamoxifen. As long as a patient is making an informed and preference-based decision, I believe their physicians have partnered effectively in helping support her decision," Dr. Griggs added.

Information explaining the updated recommendations and what they mean for patients is available at www.cancer.net/recommendations.

J Clin Oncol. Published online May 27, 2014. Full article

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