Trastuzumab deruxtecan in previously treated HER2‐positive metastatic or unresectable breast cancer: Real‐life data from the temporary use authorization program in France.

Background: Early access program (formerly cohort Temporary Authorization for Use) was granted for trastuzumab deruxtecan (T‐DXd) in France based on DESTINY‐Breast01 trial which demonstrated its efficacy and safety in HER2‐positive metastatic/unresectable breast cancer after ≥2 anti‐HER2‐based regimens received at metastatic stage. Method s : This multicenter real‐world early access program included HER2‐positive metastatic/unresectable breast patients pretreated with at least two lines of anti‐HER2 regimens who received T‐DXd 5.4 mg/kg intravenously in monotherapy every 3 weeks. Results: Four hundred and fifty‐nine patients (median age, 58 years; hormone receptor‐positive, 67%; brain metastases, 28.1%) received T‐DXd. Before inclusion, 81.7% of patients had radiation therapy and 76.5% had undergone surgery. Median number of prior metastatic treatment lines was four (range, 2–22); 99.8% patients had received trastuzumab, 94.8% trastuzumab emtansine and 79.3% pertuzumab. Follow‐up was performed from September 30, 2020 to March 30, 2021; when the early access program stopped, the median duration of T‐DXd treatment was 3.4 (range, 0–7.8) months. In 160 patients with available tumor assessment, objective response rate was 56.7% and 12.1% had progression. In 57 patients with available brain tumor assessment, complete or partial intracranial response was reported for 35.7% patients and 5.4% had progression. A total of 17 (3.7%) patients with interstitial lung disease (ILD) was reported with no cases of ILD‐related death. Conclusions: In this early access program in patients with heavily pretreated HER2‐positive metastatic/unresectable breast cancer, T‐DXd had antitumor activity with a similar response to that reported in previous clinical studies. T‐DXd was well tolerated and no new safety signals were observed. [ABSTRACT FROM AUTHOR]