Abstract

1006 Background: In the primary analysis of the Phase 3 TROPION-Breast01 study (NCT05104866), Dato-DXd showed a statistically significant and clinically meaningful improvement in progression-free survival vs investigator’s choice of CT (ICC) (HR 0.63 [95% CI 0.52‒0.76]; p<0.0001) (Bardia et al, ESMO 2023). Here we report PROs from TROPION-Breast01. Methods: Patients with inoperable or metastatic HR+/HER2‒ BC, with disease progression on endocrine therapy and for whom endocrine therapy was unsuitable and who had received 1‒2 prior lines of systemic CT, were randomized 1:1 to Dato-DXd (6 mg/kg Q3W, n=365) or ICC (eribulin/vinorelbine/capecitabine/gemcitabine, n=367). PROs were measured at prespecified timepoints, including secondary PRO endpoints of time to deterioration (TTD) in global health status (GHS)/QoL, physical functioning, and pain based on EORTC QLQ-C30, and exploratory PRO endpoints based on additional questionnaires. Results: PRO questionnaire compliance was 82.5% at baseline in both arms and remained similar across arms over time. TTD was delayed in Dato-DXd vs ICC arms for all secondary endpoints. In an analysis of time to first deterioration (primary analysis), median TTD (HR [95% CI]) in GHS/QoL was 3.4 vs 2.1 months (0.85 [0.68–1.06]), physical functioning was 5.6 vs 3.5 months (0.77 [0.61–0.99]), and pain was 3.5 vs 2.8 months (0.85 [0.68–1.07]); in an analysis of time to confirmed deterioration (sensitivity analysis), median TTD in GHS/QoL was 9.0 vs 4.8 months (0.76 [0.58–0.98]), physical functioning was 12.5 vs 6.2 months (0.77 [0.59–1.01]), and pain was 9.0 vs 5.5 months (0.72 [0.55–0.94]). The Table shows TTD in other selected functioning and symptom scales from EORTC. Patient-reported symptomatic AEs (measured by PRO-CTCAE and EORTC) were generally consistent with clinician-reported safety data, and patient-reported treatment tolerability (measured by PGI-TT) was comparable between arms. Conclusions: In TROPION-Breast01, TTD was delayed in the Dato-DXd vs ICC arms for GHS/QoL, physical functioning, pain, and most other symptoms and functioning scales. PRO data complement the improvement in efficacy and manageable safety profile demonstrated with Dato-DXd vs ICC in the primary analysis, supporting Dato-DXd as a potential new, well tolerated therapeutic option in this setting. Clinical trial information: NCT05104866 . [Table: see text]