Results of a patient-level pooled analysis of three studies of trastuzumab deruxtecan in HER2-positive breast cancer with active brain metastasis.

BACKGROUND

Brain metastases (BMs) are common in human epidermal growth factor receptor 2 (HER2)-positive advanced breast cancer, increasing morbidity and mortality. Systemic therapy for BMs can be effective, with the triple combination of trastuzumab, capecitabine, and tucatinib being a potential standard. More recently, intracranial activity of antibody-drug conjugates has been reported, but the size of individual studies has been small. Therefore, this patient-level pooled analysis was conducted.

PATIENTS AND METHODS

This is a patient-level pooled analysis of the prospective phase II DEBBRAH and TUXEDO-1 trials and the retrospective DFCI/Duke/MDACC cohort. Patients with evaluable active BMs (defined as newly diagnosed and untreated or progressing with measurable tumor-related size after previous local therapy) from HER2-positive breast cancer (BC) and treated with trastuzumab deruxtecan (T-DXd) included in these studies were eligible. The primary endpoint was intracranial objective response rate (ORR-IC) by Response Assessment in Neuro-Oncology (RANO)-BM criteria.

RESULTS

Overall, 37 patients were assessable for intracranial response assessment. BMs progressing after prior local therapy were present in 64.9% of patients. The median patient age was 49.1 years. All patients had received prior trastuzumab and the median number of prior systemic treatment lines was 3 (0-13). The pooled ORR-IC by RANO-BM criteria was 64.9% [95% confidence interval (CI) 47.5% to 79.8%] with low heterogeneity observed between the studies included. The clinical benefit rate by RANO-BM was 81.1% (95% CI 64.8% to 92.0%). The median progression-free survival was 13.3 months (95% CI 8.4-22.6 months) and the median overall survival was 22.5 months (95% CI 14.9 months-not achieved) with high heterogeneity between studies and numerically longer in patients with few prior treatment lines. Quality of life remained stable throughout treatment, with no new safety concerns.

CONCLUSIONS

This patient-level pooled analysis of DEBBRAH, TUXEDO-1, and the DFCI/Duke/MDACC cohort indicates clinically relevant intracranial activity of T-DXd in patients with active HER2-positive BC, BMs, and extensive systemic pretreatment. The results therefore support the use of T-DXd when clinically indicated irrespective of BMs.