New Hormone Therapy Extends Remission in Early-stage Hormone Receptor-positive Breast Cancer

PEOPLE WITH EARLY-STAGE hormone receptor-positive breast cancer often receive maintenance hormone therapy, such as aromatase inhibitors or a selective estrogen receptor modulator, to reduce the risk of cancer recurrence. These treatments, taken for five to 10 years, reduce risk by blocking or reducing estrogen in the body.

Data presented Dec. 10 at the 2025 San Antonio Breast Cancer Symposium (SABCS) suggest an investigational selective estrogen receptor degrader (SERD) called giredestrant could do a better job at keeping cancer from returning in people who are treated for early-stage disease. Currently, SERDs, which are a type of hormone therapy that block and break down estrogen receptors, are only approved for use in metastatic breast cancer.

Aditya L. Bardia, a physician-scientist at the UCLA Jonsson Comprehensive Cancer Center in Los Angeles who presented the findings, described the study as a “pivotal moment,” since the research suggested a new maintenance hormone therapy in early-stage disease for the first time in 25 years.

The phase III lidERA Breast Cancer trial included 4,170 people with stage I, II or III HER2-negative, estrogen receptor-positive breast cancer who received chemotherapy, if indicated, and surgery. For maintenance treatment, half of the participants received giredestrant, while the other half received any of four standard-of-care endocrine therapies that are currently used to reduce the risk of breast cancer recurrence. Sixteen percent of patients received the selective estrogen receptor modulator tamoxifen, which blocks estrogen receptors, and 84% received the aromatase inhibitors.

Using data based on a median follow-up of 32 months, researchers calculated a 92.4% three-year invasive disease-free survival rate for people who received giredestrant and 89.6% for those who received standard therapy. In those who received the novel SERD, researchers calculated a 94.4% distant recurrence-free survival rate, compared with 92.1% for those who received standard endocrine therapy. (Distant recurrence-free survival tracks how long a patient remains free of metastatic recurrence—that is, cancer coming back outside the breast and lymph nodes.)

While data about overall survival were not mature, Bardia, who presented the findings at a media briefing and during a general session at SABCS, noted that current data on giredestrant showed a trend toward increased overall survival.

The oral SERD had similar side effects as standard hormone therapy. In both treatment arms, almost half of patients reported bone pain, and roughly one quarter experienced hot flashes. However, Bardia pointed out that people who took giredestrant and who experienced bone pain were less likely to stop treatment than those who were receiving standard hormone therapy.

In all, 347 people who received giredestrant discontinued treatment compared with 520 people who received the standard of care hormone therapy—a difference that could indicate giredestrant is more tolerable than current hormone therapy, Bardia said. He also said that patients who took giredestrant had higher rates of bradycardia, which is defined as slow heart rate and is a known side effect of oral SERDs.

Most patients with early-stage breast cancer now receive CDK4/6 inhibitors with hormone therapy as part of maintenance treatment, said Lisa A. Carey, a physician-scientist at UNC Lineberger Comprehensive Cancer Center in Chapel Hill, North Carolina who was a discussant during the session.

Based on five- and seven-year data from CDK4/6 inhibitor trials, the addition of a CDK4/6 inhibitor to standard hormone therapy has increased invasive disease-free survival rates by about 4.5 to 6.5 percentage points in stage II and III breast cancer, who made up the majority of people on the trial, Carey added. She said that, if the oral SERD became available, giredestrant might be an option for patients who were unable to tolerate CDK4/6 inhibitors. Doctors might also consider using a SERD for certain patients after they finished the standard two to three years of treatment with a CDK4/6 inhibitor and hormone therapy. “I say that with some trepidation because this was not how the study was designed, but these are practical considerations,” Carey said. An ongoing sub-study that is part of lidERA will also be examining the addition of the CDK4/6 inhibitor Verzenio (abemaciclib) to giredestrant for early-stage breast cancer.

Carey also questioned how much a new SERD in early-stage cancer would cost, given the cost of new oral SERDS in the metastatic setting. “Efficacy is better [than other hormone therapies], toxicity is no worse, but cost is a concern,” Carey said, as she presented a slide with the monthly wholesale costs for new SERDs at more than $22,000 a month. In comparison, standard hormone therapies were all under $1,000. “We should all acknowledge that there is a large potential impact on the national health care system if giredestrant is priced similar to oral SERDs that are given in the metastatic setting.”

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