A recent study conducted in Germany showed a decrease in estradiol levels in men treated for hormone receptor-positive breast cancer, using a gonadotropin-releasing hormone analogue (GnRHa) with tamoxifen or an aromatase inhibitor (AI). The results of this study were published in JAMA Oncology.

The study was the randomized phase 2 MALE clinical trial (ClinicalTrials.gov: NCT01638247) in which 56 patients were allocated across 3 arms for 6 months of treatment with the arms consisting of tamoxifen only, tamoxifen with a GnRHa, or an AI with a GnRHa. The change from baseline to 3 months in 17-β-estradiol levels was the primary endpoint. Multiple secondary endpoints also were evaluated.

Treatment was begun in 52 patients, and 1 patient per arm discontinued therapy early. The median age of patients who started therapy was 61.5 years (range, 37 to 83).

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There were 50 evaluable patients for the analysis of the primary endpoint, with 17 receiving tamoxifen alone, 15 receiving tamoxifen with a GnRHa, and 18 receiving a GnRHa with exemestane as the AI. The study investigators reported a median 3-month increase in 17-β-estradiol levels by 67% (or +17.0 ng/L) for patients receiving tamoxifen only, a median 85% decrease (–23.0 ng/L) for patients receiving tamoxifen with a GnRHa, and a median 72% decrease (–18.5 ng/L) for those receiving an AI with a GnRHa (P <.001).

Percent changes in 17-β-estradiol levels at 6-months were +41% (+12.0 ng/L) with tamoxifen alone, –61% (–19.5 ng/L) with tamoxifen and a GnRHa, and –64% (–17.0 ng/L) with an AI plus a GnRHa (P <.001). The study investigators reported that there were also improvements in sexual function and quality of life for the study arms that included a GnRHa, but that there were no changes in these parameters for patients receiving tamoxifen alone.

“The addition of GnRHa to [an] AI or tamoxifen leads to a more profound suppression of estradiol, which is known to increase survival in premenopausal women,” the study investigators concluded in their report.

Disclosures: Several study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.


Reinisch M, Seiler S, Hauzenberger T, et al. Efficacy of endocrine therapy for the treatment of breast cancer in men: results from the MALE phase 2 randomized clinical trial. JAMA Oncol. 2021;7(4):565-572. doi:10.1001/jamaoncol.2020.7442