Effectiveness and Safety of Different Estradiol Regimens in Transgender Women (TREAT Study): Protocol for a Randomized Controlled Trial

Background Current guidelines for gender-affirming hormone therapy (GAHT) for transgender women are mostly based on clinical experience from experts in the field and treatments used on postmenopausal women. While care is currently provided with the best available evidence, there is a critical gap in knowledge about the safest and most effective estradiol routes of administration for GAHT in transgender women; this statement is supported by the World Professional Association for Transgender Health on their Standards of Care for the Health of Transgender and Gender Diverse People, version 8. Furthermore, the reported rates of cardiometabolic adverse events in transgender women highlight the importance of investigating changes in lipoproteins, glucose, and insulin sensitivity, among other markers while receiving GAHT. Objective This study aims to evaluate the degree of testosterone suppression achieved at 1, 6, and 12 months in treatment-naive transgender women when randomized to GAHT with estradiol and spironolactone as antiandrogens. As a secondary aim, this study will assess the treatment effect on metabolic and coagulation factors from baseline to 6 and 12 months after initiating GAHT. Methods This is a prospective pilot, open-label, randomized clinical trial conducted at an adult transgender clinic in a tertiary medical center. The 3 treatment arms include once-daily sublingual 17-β estradiol, twice-daily sublingual 17-β estradiol, and transdermal 17-β estradiol. All participants received spironolactone as an antiandrogen. Transgender women aged 18 to 45 years who are being evaluated for the initiation of GAHT with 17-β estradiol and did not have a history of coagulopathy, cigarette smoking, liver disease, dyslipidemia requiring treatment, or use of gonadotropin-releasing hormone agonist were eligible to enroll. The main outcome is the total testosterone suppression at 1 and 6 months after the initiation of GAHT, and the secondary outcome is to assess treatment effect in a lipid panel; homeostatic model assessment for insulin resistance; coagulation factors II, IX, and XI; Von Willebrand factor; activated protein C resistance; protein C; and protein S at baseline, 6 months, and 12 months after therapy is initiated. Results This study was funded in March 2022, and enrollment concluded in August 2022. It was concluded in July 2023, and currently, the results are being analyzed for publication. Conclusions The Transgender Estradiol Affirming Therapy (TREAT) study offers a rigorous and reproducible approach to answer important questions regarding GAHT in transgender women, specifically, the most effective 17-β estradiol regimen to suppress testosterone levels to 50 ng/dL, as currently recommended. Trial Registration ClinicalTrials.gov NCT05010707; https://clinicaltrials.gov/study/NCT05010707 International Registered Report Identifier (IRRID) DERR1-10.2196/53092


Strengths
Reviewer 1: • This is a feasibility study that aims to study dosing regimens and safety profiles of estrogen formulations in transgender females.This is an understudied population and the field certainly needs more evidence-based guidance.• Excellent preliminary data assessing patient interest in participation and thus feasibility of study completion.
• Detailed 2 year evaluation of anthropomorphic and laboratory testing in order to gather preliminary data in order to guide data collection in future larger studies.
Reviewer 2: • This study addresses an important problem in a marginalized and understudied population (i.e., the lack of research on gender affirming hormone therapy represents a critical gap in knowledge that precludes the delivery of safe and appropriate transgender care.)• Results from this research will provide prelim data for studies that can generate evidence and inform standards in clinical care.This is highly significant work.• The research compares three treatments which are administered regularly, despite inadequate evidence.
• The PI serves as the Co-Director of the Transgender Center at Wash U, positioning him perfectly for this research.Dr. Nicol (Co-I) has extensive experience conducting clinical trials studying pharmacotherapies in youth and young adults.• The approach clearly spells out inclusion and exclusion criteria, the experimental design, and the protocol.
• The scientific environment is excellent.
Reviewer 3: • Addresses critical disparities in care.In the absence of preliminary data, the qualitative patient engagement data adds to the feasibility of the proposed study.

Weaknesses Reviewer 1:
• There is extensive laboratory evaluation every 6 months.Only some of these are included in the budget.I assume that the rest are standard of care and are part of the clinical evaluation, but some clarification on which tests are experimental and which are standard of care would benefit the reader.• There is a paucity of preliminary data, although this is not necessarily a weakness in the setting of a feasibility study and is certainly addressed by the PI.
Reviewer 2: • The requested study period is wrong...beginning date is 3/31/22 and not 8/3/21.The application describes that the project will take longer than one year (the study period).• Proposal has several typos and appears spellcheck not used.
• Dr. Nicol's biosketch says that this research will support "the career development of a promising physicianscientist in pediatric endocrinology, Samuel Cortez," yet Dr. Cortez was not mentioned anywhere else on the application or budget.• The authors seem to use the terms efficacy and effectiveness interchangeably.Is this an efficacy trial determining results under ideal circumstances?Or an effectiveness trial -or pragmatic trial -measuring the degree of beneficial effect under real-world conditions?The authors need to choose one and stick with it.• The application is titled "Effectiveness, safety, and tolerability of different estradiol dosing regimens in transgender females" yet the investigators do not spell out what measures are effectiveness, safety, or tolerability.They could connect the dots for the reviewer a bit more clearly.
Reviewer 3: • Aims seem feasible in 1-year, but proposed timeline is 2 years.It would be helpful to better describe the purpose for the additional year of follow-up.Will enough data be collected within 1-year to support next stage funding?

Recommendations for Improvement
Reviewer 1: • Consider assessing patient satisfaction and tolerability/side effect profiles with regimens as well.Although this may be more relevant as an outcome in a larger RCT, survey administration feasibility is also important to address.

ICTS BIOSTATISTICS, EPIDEMIOLOGY AND RESEARCH DESIGN (BERD) Review Comments
• Weaknesses: I have moderate epidemiological or biostatistical concerns for this study.
The randomized feasibility trial appears to be well-designed.As a minor point, the exclusion criteria are fairly restrictive (i.e., no smokers or obese participants), but this may be appropriate at this stage of investigation.
As moderate methodologic concerns, the trial is described as a two-year study, but only data from the 6-month follow-up visit will be available on all or most participants during the 1-year ICTS grant period, assuming that it takes <6 months to recruit all participants.In addition, the outcome measures of the trial were not clearly described.For Aim 1, I assume that the outcome will be testosterone concentration (or possibly % testosterone suppression) at the 6-month follow-up visit, but this was not clear.For Aim 2, I assume that the outcomes will be concentrations of estrone, thrombogenic factors, and differences between concentrations of baseline and 6month metabolic factors.Finally, the rationale for the sample size was not described -i.e., what does the study have the appropriate sample size to do? Estimate a sufficiently precise measure of feasibility?Generate preliminary estimates of efficacy that would be useful to inform the sample size for a future, sufficiently powered trial?Without this information, it is difficult to understand the likely utility of the study.

Health equity comments (if applicable)
• The research team should ensure recruitment efforts include outreach to Black and other minority transgender females so that the study does not result in bias towards only white transgender females.