Open Menu
Meetings & Education
Meetings & Education
Research & Data
Practice & Patients
Career Development
News & Initiatives
Get Involved
Acolbifene vs tamoxifen for breast cancer prevention in premenopausal women at high risk for breast cancer.
Background: The TAM01 trial of low dose (5 mg) tamoxifen (LDTAM) vs placebo was associated with significant improvement in risk for breast cancer in postmenopausal women with a hazard ratio of 0.30 along with a favorable side effect profile. Risk reduction in premenopausal women was less clear, with a non-significant hazard ratio of 0.73. Tamoxifen in premenopausal women can induce substantial increases in systemic estradiol and in preclinical studies upregulate endocrine resistance gene AGR2. Both phenomena may impact LDTAM efficacy in premenopausal women. A pilot study (NCT00853996) of 20 mg/d of the SERM acolbifene in premenopausal women was associated with reduction in mammographic density, benign breast tissue Ki-67, and estrogen response gene expression (Fabian et al; Cancer Prev Res 2015) with no increase in AGR2 or vasomotor symptoms. Further studies of LDTAM and acolbifene in premenopausal women are warranted assessing change in imaging and benign breast tissue risk biomarkers with change in systemic hormones, ovarian reserve, and drug metabolites.
Methods: NCT05941520 is a randomized, double-blind Phase II trial performed as part of the University of Michigan Early Phase Clinical Cancer Prevention (ClinCaP) Consortium part of the Cancer Prevention Clinical Trials Network (CP-CTNet) comparing 6 months of tamoxifen 5 mg and acolbifene 20 mg. Eligible participants are premenopausal women â„35 without prior invasive breast cancer, but with â„ 2-fold increased risk for the disease.
The primary endpoint is difference in change in levels of AGR2 mRNA between the two arms. Secondary endpoints are within-arm change in an endocrine response gene index (ERGI), mammographic density, and MENQOL. Exploratory endpoints include within-arm change in benign breast Ki-67, ER, PR and AGR2 protein, association of baseline Anti-Mullerian Hormone (a measure of ovarian reserve) with 6-month serum estradiol and change in tissue estrogen responsive gene expression and AGR2.
Based on the preliminary data, mean log base2 (fold change, FC) of AGR2 in the acolbifene arm is assumed to be -1, which is tantamount to a 50% reduction. The estimated SD of the log2(FC) is 2.25. Assuming a log2(FC) of +0.6 in the low dose tamoxifen arm (50% increase), and the same SD as in the acolbifene arm, 36 evaluable subjects per arm are required to detect, with 80% power at an alpha = 0.03 (two-sided), a difference in FC of this magnitude between the two arms. Secondary endpoints are assessed via paired samples t-test or Wilcoxon signed-rank test.
Target enrollment in this 4-site trial is 80 over 2.5 years. The protocol opened for accrual at the University of Kansas Medical Center in October 2024 and as of January 2025 is pending activation at the other sites.
Disclaimer
This material on this page is ©2025 American Society of Clinical Oncology, all rights reserved. Licensing available upon request. For more information, please contact licensing@asco.org
Author Details
Carol Fabian
Department of Medicine Medical Oncology and Precision Prevention, University of Kansas Medical Center, Westwood, KS
Authors chevron_right
Associated Organizations chevron_right
Abstract Details
Meeting
2025 ASCO Annual Meeting
Session Type
Poster Session
Session Title
Prevention, Risk Reduction, and Genetics
Track
Prevention, Risk Reduction, and Genetics
View MoreAbstract Disclosure
open_in_new
Similar Abstracts
text_snippet
Abstract
2022 ASCO Annual Meeting
First Author: Soong June Bae
text_snippet
Abstract
2015 ASCO Annual Meeting
First Author: Fröydis Nyborg Fjeldheim
text_snippet
Abstract
2022 ASCO Annual Meeting
First Author: Megan Elizabeth Tesch
text_snippet
Abstract
2022 ASCO Annual Meeting
First Author: Soo Yeon Baek
Your Privacy
ASCO is committed to transparency regarding our websites and the ways we process data. When you visit our site, we may store or retrieve information on your browser, mostly in the form of cookies. This information might be about you, your preferences, your location, or your device and is mostly used to make the site work as you expect it to and to personalize your web experience with us.
Because we respect your right to privacy, you can choose not to allow some or all types of cookies. Click on the different category headings to find out more about the types of cookies used on our websites and change your default settings to match your preferences. Please read these carefully. Blocking some types of cookies may impact your experience on the site, including our ability to personalize the content you receive from us.
For a full explanation of the personal and non-personal information we collect on our site, including how we use that information and your rights regarding that information, please review our Privacy Policy. Use of our website is also subject to our Terms of Use.
Allow All
Manage Consent Preferences
Essential Website Cookies
Always Active
These cookies are necessary for the website to function and are sometimes referred to as âstrictly necessaryâ cookies. They make sure the website delivers you information and services in an optimal way.
They are often set in response to an action you take, such as changing your cookie preferences, setting your privacy preferences, logging in to our website, asking the site to remember you on subsequent pages, or filling in forms. These cookies do not identify you personally.
You can set your browser to block or alert you about all cookies, including essential website cookies, but some parts of the site will not work as a result.
Cookies Detailsâ
Performance and Functionality Cookies
Performance and Functionality Cookies
These cookies enhance the performance and functionality of our websites and the services we provide. For example, these cookies can keep track of your visitor session in between visits, enable you to share content through social media, use embedded media players, and use comment features. They also help us balance website load and improve site speed and performance.
All information these cookies collect is aggregated and therefore anonymous. These cookies may be set by us or by third party providers whose services we have added to our websites. These cookies are non-essential, but without these cookies, certain functionality or enhanced features may become unavailable.
Cookies Detailsâ
Personalization and Analytics Cookies
Personalization and Analytics Cookies
These cookies collect information that is used to help us understand how our websites and content are used, help us customize our websites and application for you in order to enhance your experience, and help us improve the content that ASCO creates to better meet our membersâ and visitorsâ needs. Examples include cookies that show us which content might be most popular with our visitors, understand browsing history of our users, understand the effectiveness of our own advertising, and enable us to recommend content to individual users based on their profile and activities on the website.
These cookies may be set by us or by third party providers whose services we have added to our websites.
These cookies are non-essential to the functionality of the site and may contain information that enables us or our third party providers to identify you and build a profile of your interests. Without these cookies, you will not be able to have a customized or personalized experience within our website.
Cookies Detailsâ
Advertising Cookies and Social Media Cookies
Advertising Cookies and Social Media Cookies
Advertising (or Targeting) cookies are third party cookies that may be set through our site by our advertising partners. They may be used by those companies to build a profile of your interests and show you relevant ads on other sites.
Social Media Cookies are cookies set by a range of social media services that we have added to the site to enable you to share our content with your friends and networks. They are capable of tracking your activities across other sites and building a profile of your interests. This may impact the content and messages you see on other websites you visit.
These cookies and the data collected by the third parties may be combined with data from other users or data about your activity on other sites. While the data collected on our site is aggregate or non-personal, the data may be used by such third parties to link you on other platforms or otherwise identify you.
If you do not allow these cookies, you may experience less targeted advertising.
Cookies Detailsâ
Back Button
Cookie List
Search Icon
Filter Icon
Clear
checkbox labellabel
ApplyCancel
ConsentLeg.Interest
checkbox labellabel
checkbox labellabel
checkbox labellabel
View Cookies
Name
cookie name
Save Settings
Download