on PinterestNew research found that the drug endoxifen reduced mammographic breast density with fewer side effects.
on PinterestNew research found that the drug endoxifen reduced mammographic breast density with fewer side effects. praetorianphoto/Getty Images
- A study has found promising results with the breast cancer prevention drug (Z)-endoxifen.
- The drug reduced breast density safely and with fewer side effects than tamoxifen.
- It also had fewer troublesome side effects than this standard preventive treatment.
- Experts say that if further research confirms these findings, the endoxifen could help increase compliance and improve outcomes.
Nearly half of all females ages 40 and older have dense breasts, which can impact breast cancer risk.
A clinical trial published in the Journal of the National Cancer Institute on April 27 revealed promising results for a new breast cancer prevention approach targeting breast density.
The protocol involves low doses of (Z)-endoxifen, a metabolite of the well-known drug tamoxifen.
The study, known as the KARISMA Endoxifen trial, tested the effects of two daily doses of (Z)-endoxifen on mammographic breast density, a known marker of breast cancer risk and treatment response.
Researchers examined whether (Z)-endoxifen could reduce breast density safely and with fewer side effects than tamoxifen, potentially offering a new option for breast cancer prevention. Here’s what they found.
Studying the effects of endoxifen on breast density
The KARISMA Endoxifen trial was a double-blind, randomized, placebo-controlled phase II study that enrolled premenopausal women ages 40 to 55.
Researchers recruited 240 healthy participants from Sweden’s national breast cancer screening program between December 2021 and November 2023.
To be eligible, participants needed to have regular menstrual cycles or confirm premenopausal status via blood tests, and to have a baseline mammogram showing measurable breast density. Women taking medications that could interfere with endoxifen metabolism were excluded.
Participants were randomly assigned to one of three groups receiving daily oral capsules for six months: a placebo, 1 milligram (mg) of (Z)-endoxifen, or 2 mg of (Z)-endoxifen.
The study was “double-blinded,” meaning neither the participants nor the researchers knew who was receiving which treatment until the trial was completed, ensuring unbiased results.
Mammographic breast density was measured from full-field digital mammograms obtained at the start, 3 months, 6 months, or upon early discontinuation. A specialized automated method, STRATUS, assessed breast density area in square centimeters, and images were aligned to reduce measurement errors.
Safety and tolerability were evaluated throughout the study by monitoring vital signs and blood chemistry, and by assessing participant-reported side effects via a digital application and questionnaires.
Tolerability was assessed using the Breast Cancer Prevention Trial Eight Symptom Scale (BESS Plus), a validated symptom questionnaire, supplemented with questions specific to tamoxifen-related symptoms based on previous research.
The trial’s main goal was to determine whether either dose of (Z)-endoxifen was better than placebo at reducing mammographic breast density, a proxy for breast cancer risk reduction.
Statistical analysis focused on relative changes in breast density adjusted for baseline values and compared the results between placebo and active treatment groups.
Endoxifen reduced breast density with fewer side effects
Of the over 126,000 females invited to participate, 240 were enrolled and randomly assigned to the three treatment groups, with 75 females in each group completing baseline and end-of-treatment
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