Deep Academic Interpretation
At the recent 2026 ASCO Annual Meeting, Professor Peter Schmid, representing the lidERA study group from the Barts Cancer Institute, Queen Mary University of London, detailed the efficacy and safety analysis results based on menopausal status (pre/perimenopausal vs. postmenopausal) from the Phase III lidERA BC clinical trial. The study aims to evaluate the clinical value of Giredestrant (GIRE), a next-generation oral selective estrogen receptor degrader (SERD), in the adjuvant treatment of patients with estrogen receptor-positive (ER+), HER2-negative (HER2-) early breast cancer (eBC).01 Research Background: Challenges of Adjuvant Endocrine Therapy and the Rise of Oral SERDs
In the adjuvant treatment of ER+/HER2- early breast cancer, although aromatase inhibitors (AI) and Tamoxifen have significantly improved patient prognosis, some high-risk patients still face the risk of invasive disease recurrence. Furthermore, side effects associated with traditional endocrine drugs (such as musculoskeletal pain and hot flashes) lead to approximately 20%-30% of patients struggling to adhere to the 5-10 year treatment course, which seriously impacts long-term survival benefits. Giredestrant, as a potent, non-steroidal, oral SERD, possesses high selectivity. It can directly and competitively bind to the estrogen receptor (ER), inducing its degradation and inactivation, thereby more thoroughly blocking the estrogen signaling pathway. Compared with the traditional intramuscularly injected SERD Fulvestrant, oral administration greatly improves patient compliance. The lidERA study represents its key strategic layout in the early adjuvant stage.
02 lidERA BC Study Design: Rigorous High-Risk Population Screening and Stratification
lidERA BC (NCT04505826) is a global, multicenter, randomized, open-label Phase III clinical trial that enrolled a total of 4,170 patients with Stage 1-3 ER+/HER2- early breast cancer. All enrolled patients had completed surgical resection of the primary tumor and necessary local radiotherapy and chemotherapy (if applicable). • Population Selection: Includes lymph node-positive patients, and lymph node-negative patients with high-risk features (e.g., tumor diameter >1 cm accompanied by Grade 3 differentiation, Ki-67 ≥ 20%, or high genomic test scores). • Randomization Stratification: Patients were randomized 1:1 to either the Giredestrant group (30 mg/d for 5 years) or the investigator’s choice of standard adjuvant endocrine therapy (SOC) group (including Tamoxifen, Anastrozole, Letrozole, or Exemestane). • Stratification Factors: Includes recurrence risk, geographic region, whether chemotherapy was received, and the core variable of this report—menopausal status. • Key Requirement: All pre/perimenopausal female and male patients must receive concurrent ovarian function suppression (OFS) using a gonadotropin-releasing hormone agonist (LHRH agonist) during Giredestrant or AI treatment.
03 Pre/Perimenopausal Subgroup: Giredestrant Significantly Reduces Recurrence Risk by 35%
Professor Peter Schmid pointed out in the report that in the lidERA study population, pre/perimenopausal patients accounted for approximately 41% (n=1,724). This group’s endocrine responsiveness and sensitivity to drug toxicity often differ from the postmenopausal population. • iDFS Benefit: Data showed that in the pre/perimenopausal population, the Giredestrant group demonstrated strong clinical benefit. Compared with standard endocrine therapy (SOC), Giredestrant significantly improved invasive disease-free survival (iDFS), with a hazard ratio (HR) of 0.65 (95% CI: 0.51-0.84), meaning the risk of recurrence was reduced by 35%. • 3-year iDFS Rate: The 3-year iDFS rate for the Giredestrant group reached 94.0%, while the standard treatment group was only 91.5%, an absolute benefit of 2.5%. • Distant Recurrence-Free Interval (DRFI): In the most critical ability to prevent distant metastasis, Giredestrant performed even more remarkably in the premenopausal population, with the HR reaching 0.58, significantly reducing the risk of distant recurrence by 42%. • Synergistic Drug Impact: Subgroup analysis further showed that the benefits of Giredestrant were consistent whether in the baseline population receiving AI+OFS or Tamoxifen ± OFS (HR of 0.66 and 0.62, respectively).
04 Postmenopausal Subgroup: Robust Benefit Trends and Improved Long-term Prognosis
In the postmenopausal group, which accounted for 59% of the total population (n=2,446), Giredestrant also demonstrated superior efficacy compared to standard endocrine therapy. • iDFS Performance: The iDFS HR for postmenopausal patients was 0.74 (95% CI: 0.61-0.89), reducing the risk of recurrence by 26%. • 3-year Survival Comparison: The 3-year iDFS rates for the Giredestrant group and the SOC group were 91.3% and 88.3%, respectively, with an absolute difference of 3.0%. • DRFI Benefit: In this subgroup, Giredestrant’s control over distant recurrence was also superior to traditional drugs, with an HR of 0.76. Professor Schmid emphasized that although lower HR values (more obvious benefit) were seen in the premenopausal subgroup, the survival curves for both subgroups separated rapidly from the beginning of treatment and the benefit trend remained robust over time. This confirms the broad-spectrum activity of Giredestrant across the entire population, surpassing existing standard treatments.
05 Safety Features: Significant Reduction in Musculoskeletal Involvement, Enhancing Compliance
The success of adjuvant endocrine therapy largely depends on long-term patient compliance. The safety analysis of the lidERA study (especially the data shown in the Tornado Plot) provides an important reference for clinicians. • Overall Discontinuation Rate: Compared with the SOC group, the Giredestrant group had a lower rate of treatment discontinuation due to adverse events (AEs). Specifically, the proportion of treatment interruptions due to AEs was 5.3% in the Giredestrant group compared to 8.2% in the SOC group. • Musculoskeletal Symptoms (Arthralgia): Joint pain is the most common side effect of endocrine therapy and the primary reason for treatment discontinuation. In the lidERA study, regardless of menopausal status, the proportion of treatment discontinuation due to musculoskeletal pain in the Giredestrant group was significantly lower than in the AI group. o In the premenopausal population, the discontinuation rate due to this side effect was only 1.5% (GIRE group), significantly lower than the 5.0% in the AI group. o In the postmenopausal population, these values were 1.7% (GIRE group) and 4.3% (AI group), respectively. • Common AE Distribution: The most common AEs in both groups were joint pain and hot flashes, but the severity was mostly Grade 1-2. Grade 3 and above events were rare, proving the excellent tolerability of Giredestrant.
06 Conclusion and Clinical Significance: A New Foundation for Adjuvant Treatment of Early Breast Cancer
Professor Peter Schmid concluded that this subgroup analysis of the lidERA BC study represents an important milestone:
- Universality of Efficacy: Regardless of the patient’s menopausal status, Giredestrant as an adjuvant therapy is superior to current clinically recognized standard regimens (AI or Tamoxifen), and this advantage is particularly prominent among high-risk premenopausal patients.
- Precision Strike on Distant Metastasis Risk: The significant reduction in DRFI risk (42% reduction in premenopausal, 24% reduction in postmenopausal) indicates that this regimen is expected to ultimately translate into an overall survival (OS) benefit.
- Safety Advantage Empowers Long-term Management: The significantly lower rate of discontinuation due to side effects solves a major pain point in the long-term clinical use of AI drugs, especially by reducing the treatment burden caused by joint pain.
Expert Outlook:
Although the current follow-up time (median follow-up of approximately 36 months) is still in the early stages, the strong efficacy and favorable safety profile demonstrated by Giredestrant have provided strong evidence for the update of the standard of care (SOC) for HR+ early breast cancer adjuvant therapy. In the future, with more updates to long-term follow-up data, Giredestrant is expected to become the preferred choice for adjuvant endocrine therapy for high-risk ER+ patients, further rewriting clinical guidelines.
