233MO - Ovarian function suppression in HR-positive, HER2-positive breast cancer: An exploratory analysis from the HERA trial

Background

The integration of ovarian function suppression (OFS) with adjuvant endocrine therapy has shown benefit in premenopausal women with high-risk hormone receptor (HR)-positive breast cancer. However, limited data exist regarding the effectiveness of OFS in HR-positive, human epidermal growth factor receptor 2 (HER2)-positive breast cancer. Furthermore, the optimal antihormone therapy (tamoxifen or aromatase inhibitor) to pair with OFS remains unclear.

Methods

We analyzed patient-level data from the HERceptin Adjuvant (HERA) (BIG1-01; ClinicalTrials.gov identifier: NCT00045032) trial to evaluate whether adding OFS improves disease-free survival (DFS) and overall survival (OS) in premenopausal women with early HR-positive, HER2-positive breast cancer. We also assessed the prognosis based on the type of antihormone therapy (tamoxifen or aromatase inhibitor) used with OFS.

Results

The analysis included 965 patients, of which 501 (51.9%) received only tamoxifen and 464 (48.1%) received antihormonal therapy with OFS (tamoxifen [n = 269, 27.9%] or exemestane [n = 195, 20.2%]). Patients in the OFS group had significantly better 10-year DFS (OFS 70.9% vs. non-OFS 59.6%, p < 0.001) and OS (OFS 84.7% vs. non-OFS 74.0%, p < 0.001). Moreover, the addition of OFS was independently associated with improved prognosis. Among those receiving antihormonal therapy with OFS, those treated with an aromatase inhibitor demonstrated better DFS (HR, 0.44; 95% CI, 0.29-0.68; p < 0.001) and OS (HR, 0.43; 95% CI, 0.18-0.60; p < 0.001).

Conclusions

Our results support the addition of OFS to antihormonal therapy as a reasonable strategy in premenopausal women with HR-positive, HER2-positive breast cancer who are undergoing chemotherapy and HER2-targeted therapy. While the aromatase inhibitor appears to be more beneficial than tamoxifen when paired with OFS, further research is needed to determine the most effective antihormonal therapy to combine with OFS in this specific patient population.

Clinical trial identification

HERceptin Adjuvant (HERA) (BIG1-01; NCT00045032).

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.