Can lower estrogen pills protect breasts? new study investigates
NCT ID NCT01318005
First seen Jun 25, 2026 · Last updated Jun 27, 2026 · Updated 1 time
Summary
This study looked at 82 women aged 18-35 to see if birth control pills with lower estrogen cause less breast cell growth than those with higher estrogen. Participants took one of three different pills for 2-3 months, and researchers measured breast cell activity through a biopsy. The goal is to understand if certain pills might lower breast cancer risk, but this is just an early step—it only measures a marker, not actual cancer.
What this could mean
Our plain-language read of the trial. This is informational only, not medical advice or a prediction.
- Active substance
- Oral contraceptives (birth control pills) with different estrogen doses
- What this could lead to
- If successful, this could help identify birth control pill formulations that lower breast cancer risk while still protecting against other cancers.
- What could go wrong
- This is a small, completed study measuring only a marker of cell growth, not cancer itself. Results may not translate to actual cancer prevention.
This is an AI summary of the original study and may miss details. Read our disclaimer.
Study facts
What this study's own registry entry says, in plain language.
- Phase
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Not a phased trial
Phase numbers describe drug development. The registry uses this when they do not apply, as it does for trials of devices, procedures or behaviour changes, and for observational studies.
- Participants
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82 people
The number who actually took part.
- Started
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Feb 2011
- Finished
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Jun 2015
- Lead sponsor
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Other sponsor
The registry's catch-all category, for sponsors it does not file as a company, a government agency, or a research network.
Who can take part
This study's own entry requirements. Only the study team can say for certain whether you qualify.
- Ages
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18 to 35 years
- Sex
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Female participants only
- Healthy volunteers
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Accepted
You do not need to have the condition being studied to take part.
Show the full entry requirements Hide the full entry requirements
Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.
Inclusion Criteria: 1. Age 18-35 2. BMI \<30 kg/m2 3. Premenopausal with regular cycles or currently taking an OC 4. Not currently or recently pregnant or nursing (within previous 6 months) 5. Non-smoker 6. No use of antibiotics within the prior 4 weeks 7. Competent to provide written informed consent (as judged by study team) 8. Willing to adhere to the OC regimen 9. Willingness to refrain from the use of aspirin or NSAIDS 10 days pior to the biopsy appointment and one week following the biopsy procedure 10. Willing and able to refrain from use of fish oils 10 days prior to the biopsy appointment and one week following the biopsy procedure Exclusion Criteria: 1. Diabetes 2. Abnormal breast examination 3. Abnormal PT/INR and/or CBC with platelets test results (as determined by one of the study physicians) 4. History or current therapeutic or prophylactic use of anticoagulants 5. Known bleeding disorder or history of unexplained bleeding or bruising 6. History of breast cancer or previous diagnostic breast biopsy 7. Known allergy to local anesthetic
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As listed by the trial registrant
The condition terms exactly as the trial's registrant entered them.
Contacts and locations
Locations
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USC University Hospital
Los Angeles, California, 90033, United States