Effect of Metformin on Endometrial Thickness in Postmenopausal Breast Cancer Patients Receiving Tamoxifen

NCT07145827 | Completed

• 1 other identifier: UU-TAM-MET-2024-01
• Study Type: interventional
• Target: 60
• Locations: 1 country
• Sites: 1

Brief Summary

The goal of this clinical trial is to learn if metformin can reduce the increase in endometrial thickness caused by tamoxifen in women with estrogen-positive breast cancer taking tamoxifen for more than 1 year. It will also learn about the safety of taking metformin with tamoxifen. The main questions it aims to answer are:

1. 1.Does metformin decrease endometrial thickness in women receiving tamoxifen?
2. 2.What medical problems do participants have when taking metformin with tamoxifen?
3. 3.Take metformin daily along with tamoxifen, or take tamoxifen with placebo.
4. 4.Acquire baseline assessment and then visit the clinic at 3 months, 6 months, 9 months and 12 months for checkups and trans abdominal ultrasound test for endometrial thickness, and to be monitored for any side effects or complications.

Conditions

Breast Cancer; Endometrial Hyperplasia and Endometrial Cancers

Keywords

Metformin; Tamoxifen; Breast cancer; endometrial hyperplasia

Outcome Measures

Primary Outcomes (1)

• Change in endometrial thickness

  Endometrial thickness will be measured using transabdominal ultrasound (in millimeters) by a trained radiologist. The primary outcome is the difference in endometrial thickness between the metformin plus tamoxifen group and the placebo plus tamoxifen control group.

  Baseline, 3 months, 6 months, 9 months, and 12 months from enrollment

Study Arms (2)

Tamoxifen + Metformin

EXPERIMENTAL

Participants in this arm (n=30) will continue taking the standard oncological tamoxifen dose as prescribed and receive an addition of metformin 500mg twice daily, titrated to tolerance, during the 12-month study period.

Drug: Metfomin; Drug: tamoxifen

Tamoxifen + Placebo

PLACEBO COMPARATOR

Participants in this arm (n=30) will continue to receive the standard oncological dose of tamoxifen as prescribed, in addition to a placebo tablet matching the shape size and color of metformin tablet twice daily during the 12 months study period; they will act as the control group.

Drug: tamoxifen; Drug: Placebo matching Metformin

Interventions

Metfomin DRUG

Metformin Tab. 500mg twice daily for 12 months (titrated to tolerance if needed).

Tamoxifen + Metformin

tamoxifen DRUG

Standard prescribed oncological dose.

Tamoxifen + Metformin; Tamoxifen + Placebo

Placebo matching Metformin DRUG

An inert, film-coated tablet identical in appearance and packaging to metformin 500 mg (same size, shape, color, coating, weight, and dosing schedule), manufactured without active ingredient using standard excipients (e.g., microcrystalline cellulose, starch/croscarmellose, povidone, magnesium stearate) and identical film coat (e.g., hypromellose, polyethylene glycol, titanium dioxide). Packaged in sealed blisters to minimize odor/taste cues. Dispensed by the investigational pharmacy per randomization; to be taken twice daily"

Tamoxifen + Placebo

Eligibility Criteria

• Sex: female
• Healthy Volunteers: No
• Age Groups: Child (0-17), Adult (18-64), Older Adult (65+)

You may qualify if:

• Postmenopausal Female patients (amenorrhea ≥ 12 months).
• Histologically proven (Estrogen-positive) breast cancer.
• Completed all required surgery and/or chemotherapy (if indicated)
• On adjuvant tamoxifen for at least 1 year.
• Accepts to enroll in the study

You may not qualify if:

• Refusing to enroll in the study
• Ongoing or History of: endometrial or ovarian malignancy
• Concurrent hormonal therapy that might affect endometrial thickness
• Concurrent Diabetes mellitus in which metformin is prescribed.
• Known hypersensitivity or severe intolerance to metformin

Sponsors & Collaborators

• Uruk University: lead

Study Sites (1)

Baghdad Medical City / Department of Oncology

Baghdad, Baghdad Governorate, 10045, Iraq

Location

MeSH Terms

Conditions

Breast Neoplasms; Endometrial Hyperplasia; Endometrial Neoplasms

Interventions

Tamoxifen

Condition Hierarchy (Ancestors)

Neoplasms by Site; Neoplasms; Breast Diseases; Skin Diseases; Skin and Connective Tissue Diseases; Uterine Diseases; Genital Diseases, Female; Female Urogenital Diseases; Female Urogenital Diseases and Pregnancy Complications; Urogenital Diseases; Genital Diseases; Uterine Neoplasms; Genital Neoplasms, Female; Urogenital Neoplasms

Intervention Hierarchy (Ancestors)

Stilbenes; Benzylidene Compounds; Benzene Derivatives; Hydrocarbons, Aromatic; Hydrocarbons, Cyclic; Hydrocarbons; Organic Chemicals

Study Officials

• Ghasak Kais Abdulhussain, BSc, MSc, PhD (Pharmacology)

  Uruk University

  PRINCIPAL INVESTIGATOR

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: DOUBLE
• Who Masked: PARTICIPANT, OUTCOMES ASSESSOR
• Masking Details: This is a double-blind study. Neither the participants nor the ultrasound operator assessing the primary outcome (endometrial thickness) will be aware of the treatment allocation. Study medication and placebo will be identical in appearance and packaging. Randomization codes will be securely held and only revealed after completion of data analysis, unless required for patient safety.
• Purpose: PREVENTION
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Lecturer in department of Pharmacology (B.Sc , M.Sc, Ph.D) / College of Pharmacy

Study Record Dates

• First Submitted: August 18, 2025
• First Posted: August 28, 2025
• Study Start: January 2, 2024
• Primary Completion: July 1, 2025
• Study Completion: July 1, 2025
• Last Updated: September 12, 2025

Record last verified: 2025-09

Data Sharing

• IPD Sharing: Will share
• Time Frame: Upon publication of the trial result on open access repository.
• Access Criteria: Access will be open to researchers and the public via a free, open-access data repository, with a DOI provided in the publication. Data will be de-identified to protect participant privacy.

Locations

IR (1)