A Cohort Study of the Effectiveness of Trastuzumab Deruxtecan for Treating Metastatic Progressive HER2-Positive Breast Cancer.

INTRODUCTION

The FDA approved trastuzumab deruxtecan (T-DXd) for treating human epidermal growth factor receptor 2-positive (HER2+) metastatic breast cancer (mBC) based on the phase II trial DESTINY-Breast01. The phase III trial DESTINY-Breast03 confirmed the efficacy of T-DXd with improvements in progression-free survival (PFS) (HR = 0.33) and overall survival (OS) (HR = 0.64) compared with trastuzumab emtansine (T-DM1).

PATIENTS AND

METHODS

This is a retrospective, single-institution, effectiveness study of patients with HER2+ mBC treated with T-DXd. Data were summarized on de-identified patients, tumors, and outcomes per treating physician. The Kaplan-Meier method was used for survival analyses. A 2-sided P value < .05 was considered statistically significant. Cox proportional hazards models were utilized. The initial model included all variables, and backward elimination was used to remove variables with P > .1 to obtain the final model.

RESULTS

Eighty-four patients with progressive HER2+ mBC with a median age of 57 years (27-78 years) were treated with T-DXd. Of the total patients, 16.7% had an ECOG Performance Status ≥2, and 69.0% had 1 or 2 prior lines of therapy for mBC. Almost half (45.2%) had received prior T-DM1, and only 69.0% started T-DXd at full dose. Median real-world PFS (rwPFS) was 13.3 months (95% CI, 11.4-16.9). No significant differences in rwPFS were observed in stratified analyses. Median real-world OS (rwOS) was 38.7 months (95% CI, 24.5-61.8).

CONCLUSION

T-DXd showed effectiveness for treating HER2+ mBC in a real-world cohort with pretreated patients.