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William J. Gradishar, MD, FACP, FASCO


Use of Lower-Dose Alternative Schedules of Exemestane in ER-Positive Breast Cancer

By: Emily Rhode
Posted: Wednesday, May 24, 2023

Adverse events can play an important role in the reluctance to implement certain preventive therapies in breast cancer. According to a study published in JAMA Oncology, a reduced dosing schedule of the aromatase inhibitor exemestane was found to be noninferior to the standard dose in reducing serum estradiol levels and thus did not increase adverse events. The authors suggested this reduced-dosing schedule be further investigated in prevention studies and in women who cannot tolerate the daily dose in the adjuvant setting.

“These data support the use of a three-times-weekly schedule for further studies of exemestane in breast cancer prevention,” said Bernardo Bonanni, MD, of the European Institute of Oncology IRCCS, Milan, Italy, and colleagues.

This multicenter, double-blind phase IIb randomized clinical trial aimed to compare the noninferiority percentage change of estradiol, a surrogate biomarker of efficacy, in postmenopausal women with estrogen receptor (ER)-positive breast cancer using different dosing schedules of exemestane. The study included 180 women with stage 0 to II breast cancer who were candidates for breast surgery. Patients were randomly assigned to three arms: exemestane once daily (n = 55), three times weekly (n = 56), or once weekly (n = 60).

Results showed that exemestane given three times weekly was noninferior to the once-daily schedule in reducing circulating estradiol in participants, whereas the once-weekly schedule was less effective. In the intention-to-treat population, the least square mean percentage change of serum estradiol was –89% for once-daily dosing, –85% for three-times-weekly dosing, and –60% for once-weekly dosing. No significant difference in estradiol percentage change was seen between the once-daily and three-times-weekly arms (P for noninferiority = .37). Compliant patients (n = 153) showed a 2%. Additionally, the secondary endpoints Ki67 index and progesterone receptor level decreased in all arms. Of note, adverse events were similar across all treatment arms.

Disclosure: For full disclosures of the study authors, visit

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