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Part 1: Understanding ESR1 mutations

December 2, 2025

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In this first part of our four-part series, Dr. Cohen, a medical oncologist, and Dr. Shanahan, patient advocate and president of Metavivor, discuss ESR1 mutations and why they may be an important part of metastatic breast cancer care.

We recently hosted a four-part discussion with Dr. Jules Cohen, a medical oncologist specializing in hematology and oncology at Stony Brook Medicine in New York, and Dr. Kelly Shanahan, a breast cancer survivor (thriver), patient advocate, and president of METAvivor, an organization dedicated to supporting people living with stage 4 metastatic breast cancer.

Together, they break down complex topics in a clear and patient-friendly way to help you feel informed, supported, and empowered throughout your metastatic breast cancer journey.

In this first part of the series, Dr. Cohen and Dr. Shanahan explain what ESR1 mutations are, how they can develop after endocrine therapy, and why testing for ESR1 mutations may be an important step in finding the most effective treatment for you.

Watch to learn:

  • what an ESR1 mutation is and how it develops

  • who may benefit from ESR1 mutation testing

  • how ESR1 mutations can influence treatment decisions

  • questions you may want to ask your care team

  • where this biomarker fits within the broader landscape of mBC care

Whether you’re newly diagnosed with metastatic breast cancer or navigating a change in treatment, this conversation offers guidance, clarity, and expert insight to help you better understand your options.

Dr. Cohen is a paid consultant of Stemline and this program has been sponsored by Stemline Therapeutics, Inc. Dr. Kelly Shanahan is the President of the Board of Directors of Metavivor, a metastatic breast cancer advocacy organization, that has received sponsorship funding from Stemline Therapeutics, Inc.

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