CHICAGO, IL—Adjuvant treatment with the aromatase inhibitor (AI) exemestane plus ovarian function suppression significantly reduced risk of disease recurrence in premenopausal women with hormone receptor (HR)–positive early breast cancer compared with tamoxifen plus ovarian function suppression (OFS), representing “a new treatment option for premenopausal women,” a joint analysis of two phase 3 trials concluded at the 2014 American Society of Clinical Oncology (ASCO) Annual Meeting.

The International Breast Cancer Study Group (IBCSG) TEXT and SOFT trials, which enrolled 5,738 women, were conducted in 27 countries in collaboration with the Breast International Group (BIG) and the North American Breast Cancer Group (NABCG) and is the first to demonstrate a role for AIs in this population, said Olivia Pagani, MD, clinical director of the Breast Unit at the Oncology Institute of Southern Switzerland in Bellinzona, Switzerland.

The aromatase inhibitor question for the two trials was: does adjuvant therapy with the AI exemestane improve disease-free survival relative to tamoxifen in premenopausal women treated with OFS for HR-positive breast cancer?

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The TEXT trial (n = 2,672) randomly assigned women within 12 weeks of surgery to 5 years of treatment with OFS and either exemestane or tamoxifen. Optional chemotherapy was administered concurrently with OFS.

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The SOFT trial (n = 3,066) randomly assigned women to 5 years of treatment with OFS plus either exemestane or tamoxifen; a third arm received tamoxifen alone. All patients were treated either within 12 weeks of surgery if no chemotherapy was planned or within 8 months of completing (neo)adjuvant chemotherapy.

The protocol treatment was for 5 years from randomization, Dr. Pagani said. In the TEXT trial, all women started with the GnRH agonist triptorelin intramuscularly every 28 days. Triptorelin was initiated concurrently with chemotherapy, if it was given. Bilateral oophorectomy or irradiation were alternatives to triptorelin after 6 months. In SOFT, OFS method was by physician choice. Oral endocrine therapy was exemestane 25 mg per day or tamoxifen 20 mg per day. In TEXT, women started treatment 6 to 8 weeks after initiation of OFS or after chemotherapy, if given. The primary endpoint was disease-free survival; secondary endpoints were breast cancer–free interval, distant recurrence-free interval, and overall survival (OS).