The effect of adding ovarian function suppression to adjuvant endocrine therapy in premenopausal patients with hormone receptor-positive, HER2-positive breast cancer who have undergone neoadjuvant therapy: a single-center experience.

PURPOSE: The role of ovarian function suppression (OFS) in premenopausal patients with hormone receptor (HR)-positive, HER2-positive breast cancer remains unclear in the era of anti-HER2 therapy. This study evaluated the effect of adding OFS to adjuvant endocrine therapy on outcomes in premenopausal patients receiving neoadjuvant anti-HER2 therapy.

METHODS: We retrospectively reviewed 138 premenopausal patients with HR-positive/HER2-positive non-metastatic breast cancer treated with anti-HER2-based neoadjuvant therapy and surgery between 2015 and 2024. Patients were grouped by receipt of OFS during the adjuvant period. The primary endpoints were disease-free survival (DFS), distant disease-free survival (DDFS), and overall survival (OS); pathological complete response (pCR; ypT0/is ypN0) was evaluated as a secondary endpoint.

RESULTS: Among 138 patients, 60 (43.5%) received OFS. Overall, 42% achieved pCR. After a median follow-up of 56 months, 20 patients (14.5%) recurred or developed metastasis, and 11 (8%) died. Five-year OS rates were 93.9% with OFS and 85.8% without (p = 0.4); DFS rates were 80.7% and 81.3% (p = 0.9). Patients with pCR had excellent survival (5-year OS 100%) irrespective of OFS. In those with residual disease, OFS was associated with numerically higher OS (89.9% vs. 77.6%) but no DFS benefit. Multivariate analysis showed no independent association between OFS and survival outcomes.

CONCLUSION: In this retrospective real-world study, no independent association between OFS and survival outcomes was observed in premenopausal patients with HR-positive/HER2-positive breast cancer treated with anti-HER2-based neoadjuvant therapy. Patients achieving pCR had excellent prognoses regardless of OFS use. Given the limited statistical power and the predominantly tamoxifen-treated cohort, these findings should be interpreted with caution. Prospective studies are warranted to better define the role of OFS in this patient population.