Reassessing hormone therapy after breast cancer

In a recent interview with Contemporary OB/GYN, Jayant S. Vaidya, PhD, professor of surgery and oncology at the University College London, and Sarah Glynne, MBBS, BSc, GP menopause specialist at The Portland Hospital, discussed current evidence and evolving perspectives on the use of hormone replacement therapy (HRT) after breast cancer.^1,2

Their discussion centered on a newly published paper in Menopause that reexamines long-held assumptions about the risks and benefits of HRT in breast cancer survivors. Historically, the use of HRT after breast cancer has been contraindicated because of the well-established link between estrogen and tumor growth.

As Vaidya explained, breast cancer often involves estrogen receptors that stimulate cancer cell proliferation. Treatments such as tamoxifen work by blocking these receptors, reducing recurrence and improving survival. Consequently, introducing estrogen through HRT has long been viewed as potentially dangerous, increasing the likelihood of relapse.

However, as Glynne noted, this creates a difficult dilemma for many survivors. Treatments that suppress estrogen can trigger severe menopausal symptoms, including hot flashes, mood changes, brain fog, joint pain, and sexual dysfunction. For some women, these symptoms are debilitating, impairing daily function and quality of life. While HRT is the most effective therapy for menopause-related symptoms, its use remains largely prohibited for women with a history of breast cancer, particularly for those with estrogen receptor (ER)–positive disease.

Glynne emphasized that breast cancer is not a uniform condition. Women with ER-negative tumors or carcinoma in situ face different risks from those with ER-positive cancers. Even among ER-positive cases, relapse risk varies widely. The researchers argue that treatment recommendations should be individualized rather than guided by a blanket prohibition.

Vaidya also revisited the 2 landmark randomized controlled trials—the HABITS and Stockholm studies—that established the foundation for current clinical guidance. These studies, halted early because higher relapse rates among women receiving HRT, showed a 6% absolute increase in recurrence risk. Yet, closer examination revealed that most of this increase involved local or contralateral breast recurrences, which are typically treatable, while the rise in life-threatening distant metastases was only approximately 0.4%.

Given advances in cancer therapies and newer forms of HRT, Vaidya and colleagues are launching the MENOABC trial to reevaluate HRT safety in contemporary settings. The study aims to better stratify risk and guide personalized decision-making through data-driven tools. Ultimately, the researchers advocate for shared, informed decisions between patients and clinicians, balancing symptom relief with individualized cancer risk.

This video is part 1 of a 2-part series. Check back tomorrow for part 2.

No relevant disclosures.

References

1. Experts call for change of heart on hormone replacement therapy after breast cancer. University College London. September 30, 2025. Accessed October 1, 2025. https://www.eurekalert.org/news-releases/1100355.
2. Glynne S, Simon J, Branson A, et al. Menopausal hormone therapy for breast cancer patients: what is the current evidence? Menopause. 2025. doi:10.1097/GME.0000000000002627