Vaginal Testosterone During Aromatase-Inhibitor Treatment: Two Different Trials

The placebo trial followed symptoms for 26 weeks

The 2018 Davis trial¹ randomized 44 women taking aromatase inhibitors after breast cancer. Thirty-seven supplied evaluable data. The compounded cream contained 300 micrograms of testosterone per dose, used nightly for two weeks, then three times weekly for 24 weeks. Placebo used the same cream base.¹

FSFI satisfaction, the primary outcome, improved over placebo by 0.73 points, with a 95% confidence interval of 0.02 to 1.43. Self-rated dryness and painful intercourse also favored testosterone, but the separate FSFI pain domain did not.¹

More placebo participants discontinued; some week-13 observations were carried forward. Australia’s National Breast Cancer Foundation funded the study. Author disclosures included pharmaceutical-company honoraria.¹

The earlier study used 5,000 micrograms per application

The 2017 Melisko study² compared testosterone cream with an estradiol ring, with 69 women completing 12 weeks. Each testosterone application contained 5,000 micrograms, substantially more than the later trial. The randomized phase II design assessed each treatment against a hormone threshold, without a head-to-head efficacy comparison.²

Persistent estradiol elevations occurred in 4 of 34 testosterone participants. Among 27 with testosterone measurements, only three remained within the study’s postmenopausal range at both follow-ups. Both treatments met the protocol’s safety threshold, which permitted persistent estradiol elevation in up to 25%. AstraZeneca funded the study.²

A hormone threshold cannot answer the recurrence question

The lower-dose trial found no significant between-group difference in measured sex steroids at week 26. Neither trial established cancer-recurrence risk over years.¹²

Newer guidance still describes substantial uncertainty

The 2025 AUA/SUFU/AUGS guideline found insufficient evidence to recommend vaginal testosterone for genitourinary symptoms of menopause. Its discussion allows that clinicians may offer it through shared decision-making, while identifying small trials, mixed results and very low certainty. An individual treatment discussion does not turn those studies into a firm recommendation.³

The Dana-Farber Breast Oncology Center⁴ consensus dated April 2026, developed after a 2023 meeting and finalized in March 2026, finds insufficient safety evidence to recommend topical testosterone after breast cancer. It starts with nonhormonal moisturizers and lubricants. These are the participating providers’ conclusions, rather than a new trial or an official institutional position.⁴

Bring the proposed formulation to both treating teams

Write down whether the difficulty is daily dryness, pain with penetration or both, plus the moisturizers tried and any irritation. If testosterone is proposed, ask your gynecologist and oncology team which formulation is intended, which symptom it should change, when they would review it and what would prompt stopping.

The “What the Prescription Options Are” section of Down There, Decoded discusses the added treatment conversation after breast cancer. Our vaginal DHEA trial review examines another hormone proposal whose symptom results and cancer-safety evidence also need separate consideration.