Estradiol Levels According to Body Mass Index in Premenopausal Patients With Breast Cancer (SIMPEC-E2)

September 16, 2026 updated by: D'Or Institute for Research and Education

Evaluation of Serum Estradiol Levels According to Body Mass Index Categories in Premenopausal Patients With Hormone Receptor-Positive Breast Cancer Receiving Aromatase Inhibitors and Pharmacologic Ovarian Suppression

his prospective observational study will evaluate whether body mass index (BMI) is associated with serum estradiol levels in premenopausal women with hormone receptor-positive breast cancer. Participants will already be receiving standard adjuvant treatment with an aromatase inhibitor and pharmacologic ovarian suppression as part of their routine clinical care. The study will not assign or modify cancer treatment.

Approximately 172 participants will be enrolled at multiple study sites in Brazil. They will be classified into two main groups: normal BMI and overweight or obesity. Clinical information, medication use, physical activity, weight, height, and serum estradiol levels will be recorded. Estradiol will be measured using an ultrasensitive laboratory method, with the main assessment occurring after approximately three months of treatment.

The primary objective is to compare the proportion of participants with serum estradiol levels above 2.72 pg/mL between the two BMI groups. The study will also examine the relationship between BMI and absolute estradiol levels and explore whether clinical characteristics, previous chemotherapy, physical activity, or use of glucagon-like peptide-1 receptor agonists are associated with inadequate estrogen suppression.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Not yet recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Detailed Description

This is a multicenter, prospective, observational cohort study designed to evaluate the association between body mass index (BMI) and serum estradiol levels in premenopausal women with hormone receptor-positive invasive breast cancer receiving adjuvant endocrine therapy with an aromatase inhibitor combined with pharmacologic ovarian suppression using a gonadotropin-releasing hormone analog.

All endocrine treatments will be prescribed as part of routine clinical care. Participation in the study will not determine the selection, dose, schedule, continuation, or modification of anticancer treatment. No experimental intervention, treatment allocation, or randomization is planned.

Approximately 172 participants will be enrolled. For the primary analysis, participants will be classified according to World Health Organization BMI categories and grouped as having normal BMI or overweight/obesity. At enrollment, demographic, anthropometric, clinical, and oncologic information will be collected, including tumor characteristics, previous cancer treatment, type and timing of aromatase inhibitor and ovarian suppression therapy, concomitant medications, physical activity, and use of glucagon-like peptide-1 receptor agonists.

Weight and height will be measured to calculate BMI. Serum estradiol will be assessed using an ultrasensitive laboratory method. A baseline estradiol measurement may be obtained when applicable, depending on the timing of enrollment. The main estradiol assessment will be performed after approximately three months of combined aromatase inhibitor therapy and pharmacologic ovarian suppression, within a protocol-defined visit window of plus or minus 14 days. If a result suggests inadequate estrogen suppression, an additional measurement may be requested within 14 days using a different laboratory method, according to institutional practice and local availability.

The primary outcome is the proportion of participants with inadequate estrogen suppression, defined as a serum estradiol concentration greater than 2.72 pg/mL after approximately three months of treatment. This proportion will be compared between participants with normal BMI and those with overweight/obesity.

Secondary and exploratory analyses will evaluate absolute estradiol concentrations across BMI categories, the correlation between BMI and serum estradiol, a potential BMI cutoff associated with inadequate estrogen suppression, and clinical characteristics associated with inadequate suppression. Exploratory subgroup analyses will consider previous chemotherapy, physical activity, and use of glucagon-like peptide-1 receptor agonists.

The primary comparison will use a chi-square test or Fisher's exact test, as appropriate. Binary logistic regression will assess the association between BMI and inadequate estrogen suppression, with BMI evaluated as both a categorical and continuous variable and adjustment for clinically relevant potential confounders. Continuous outcomes will be analyzed using parametric or nonparametric methods according to their distributions. The relationship between BMI and estradiol concentration will also be assessed using Spearman correlation, and receiver operating characteristic curve analysis will be used to explore a potential BMI cutoff associated with inadequate estrogen suppression.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Observational

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
172

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

18 years and older (Adult, Older Adult)

Accepts Healthy Volunteers

Yes

Genders Eligible for Study

Female

Sampling Method

Non-Probability Sample

Study Population

Premenopausal adult women with histologically confirmed hormone receptor-positive invasive breast cancer receiving adjuvant endocrine therapy with an aromatase inhibitor combined with pharmacologic ovarian suppression using a gonadotropin-releasing hormone analog. Potential participants will be identified during routine outpatient visits at participating oncology centers in Brazil. Participants will be classified according to World Health Organization body mass index categories and analyzed in two groups: normal body mass index and overweight or obesity.

Description

Inclusion Criteria:

Female sex. Age 18 years or older. Histologically confirmed hormone receptor-positive invasive breast cancer, defined as estrogen receptor-positive and/or progesterone receptor-positive disease, regardless of human epidermal growth factor receptor 2 status.

Premenopausal status at the initiation of ovarian suppression, as determined by menstrual history and/or laboratory criteria according to medical assessment.

Indication for adjuvant treatment with an aromatase inhibitor (anastrozole, letrozole, or exemestane) combined with pharmacologic ovarian suppression using a gonadotropin-releasing hormone analog.

Continuous use of an aromatase inhibitor and a gonadotropin-releasing hormone analog for at least 3 months before the primary study assessment.

Documented body mass index at enrollment. Ability to understand the study information and provide written informed consent.

Exclusion Criteria:

Postmenopausal status at the initiation of endocrine therapy. Known endocrine disorders that may interfere with the production or metabolism of sex steroids.

Concomitant use of medications known to interfere with estradiol metabolism or measurement, including systemic corticosteroids at supraphysiologic doses.

Metastatic disease at enrollment. Technical or logistical inability to undergo serum estradiol measurement using an ultrasensitive laboratory method.

Concurrent participation in another clinical study that may interfere with the hormonal outcomes evaluated in this study.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Observational Models: COHORT
  • Time Perspectives: PROSPECTIVE

Cohorts and Interventions

Group / Cohort

Group / Cohort

A group or subgroup of participants in an observational study that is assessed for biomedical or health outcomes.
Normal BMI

Premenopausal participants with hormone receptor-positive breast cancer receiving an aromatase inhibitor and pharmacologic ovarian suppression who have a body mass index within the normal range according to World Health Organization criteria.
Overweight or Obesity

Premenopausal participants with hormone receptor-positive breast cancer receiving an aromatase inhibitor and pharmacologic ovarian suppression who are classified as having overweight or obesity according to World Health Organization body mass index criteria.

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Percentage of Participants With Inadequate Estrogen Suppression
Time Frame: At 3 months of treatment (visit window: ±14 days)

Percentage of participants with a serum estradiol concentration greater than 2.72 pg/mL after approximately 3 months of treatment with an aromatase inhibitor and pharmacologic ovarian suppression. Serum estradiol will be measured using an ultrasensitive laboratory method. The percentage will be calculated as the number of participants with estradiol greater than 2.72 pg/mL divided by the number of evaluable participants in each body mass index group, multiplied by 100. Results will be compared between participants with normal body mass index and those with overweight or obesity.
At 3 months of treatment (visit window: ±14 days)

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Serum Estradiol Concentration by Body Mass Index Category
Time Frame: At 3 months of treatment (visit window: ±14 days)

Serum estradiol concentration, measured in pg/mL using an ultrasensitive laboratory method, will be summarized and compared across body mass index categories.
At 3 months of treatment (visit window: ±14 days)
Correlation Between Body Mass Index and Serum Estradiol Concentration
Time Frame: At 3 months of treatment (visit window: ±14 days)

The relationship between body mass index, measured in kg/m², and serum estradiol concentration, measured in pg/mL, will be assessed using Spearman's correlation coefficient. The coefficient ranges from -1 to 1, with higher positive values indicating a stronger positive association.
At 3 months of treatment (visit window: ±14 days)
Body Mass Index Cutoff Associated With Inadequate Estrogen Suppression
Time Frame: At 3 months of treatment (visit window: ±14 days)

A potential body mass index cutoff, measured in kg/m², associated with serum estradiol greater than 2.72 pg/mL will be explored using receiver operating characteristic curve analysis. The analysis will include estimation of the area under the curve, sensitivity, and specificity of the identified cutoff.
At 3 months of treatment (visit window: ±14 days)
Association Between Clinical Characteristics and Inadequate Estrogen Suppression
Time Frame: At 3 months of treatment (visit window: ±14 days)

Associations between prespecified clinical characteristics and inadequate estrogen suppression, defined as serum estradiol greater than 2.72 pg/mL, will be evaluated using binary logistic regression. Results will be reported as odds ratios with 95% confidence intervals. Evaluated characteristics may include body mass index, age, previous chemotherapy, endocrine treatment characteristics, concomitant medications, and other clinically relevant potential confounders collected according to the protocol.
At 3 months of treatment (visit window: ±14 days)
Serum Estradiol Outcomes in Prespecified Clinical Subgroups
Time Frame: At 3 months of treatment (visit window: ±14 days)

Serum estradiol concentration and the percentage of participants with estradiol greater than 2.72 pg/mL will be explored in subgroups defined by previous chemotherapy, physical activity, and use of glucagon-like peptide-1 receptor agonists. These analyses are exploratory.
At 3 months of treatment (visit window: ±14 days)

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
D'Or Institute for Research and Education

Collaborators

Collaborators

An organization other than the sponsor that provides support for a clinical study. This support may include activities related to funding, design, implementation, data analysis, or reporting.
Grupo Brasileiro de Estudos do Câncer de Mama (GBECAM)

Investigators

Investigators

A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
  • Principal Investigator: Luísa C.D.F Costa, MD, Institute of Cancer of São Paulo
  • Principal Investigator: Renata C bonadio, D'Or Institute for Research and Education (IDOR)

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
September 3, 2026

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
December 30, 2026

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
May 30, 2027

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
September 16, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
September 16, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
September 22, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
September 22, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
September 16, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
September 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • SIMPEC-ESTRADIOL-001

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

Individual participant data will not be made publicly available under the current protocol because the informed consent and data governance procedures do not provide for external sharing of individual-level clinical and laboratory data. Study findings will be disseminated in aggregate form to protect participant privacy and confidentiality and to comply with applicable ethical requirements and Brazilian data protection legislation.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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