163O Patient-reported outcomes (PROs) from DESTINY-Breast03, a randomized phase III study of trastuzumab deruxtecan (T-DXd) vs trastuzumab emtansine (T-DM1) in patients (pts) with HER2-positive (HER2+) metastatic breast cancer (MBC)

In DESTINY-Breast03 (NCT03529110), T-DXd showed superior progression-free survival by BICR vs T-DM1 (HR, 0.28 [95% CI, 0.22-0.37]; P < 0.001) and manageable safety in pts with HER2+ MBC. PRO measures incorporate pts' perspective in clinical trials to assess effect of treatment on health-related quality of life (QoL). Here, PROs and hospitalization rate for T-DXd vs T-DM1 (May 21, 2021, data cutoff) are reported. Pts with HER2+ (IHC 3+ or IHC 2+/ISH+) MBC whose disease progressed on or after trastuzumab and a taxane were assigned 1:1 to T-DXd or T-DM1. PRO endpoints were assessed before infusion on day 1 of the first 3 21-day cycles, then every 2 cycles, at end of treatment, at 40-days' follow-up, then every 3 months until end of follow-up; endpoints included European Organization for Research and Treatment of Cancer QoL questionnaires (EORTC QLQ-C30; primary variable: global health status [GHS]/QoL scale score) and the EuroQol 5-dimension 5-level (EQ-5D-5L) visual analog scale (VAS). Analyses included change from baseline (CFB) and time to definitive deterioration (TDD). Hospitalization-related endpoints were also measured. Compliance for questionnaires was >97% at baseline and >80% for cycles 3-29. QLQ-C30 baseline GHS scores recorded for T-DXd (n = 253) and T-DM1 (n = 260) were similar. At end of treatment, mean CFB was not meaningfully different vs baseline (<10-point CFB) in both arms. Median TDD of QLQ-C30 GHS was 9.7 mo for T-DXd vs 8.3 mo for T-DM1 (HR, 0.88 [95% CI, 0.70-1.11]), and all prespecified QLQ-C30 subscales presented longer TDD with T-DXd, including emotional functioning (HR, 0.69 [95% CI, 0.53-0.89]) and pain (HR, 0.75 [95% CI, 0.59-0.95]). Median TDD of EQ-5D-5L VAS was 13.2 mo for T-DXd vs 8.5 mo for T-DM1 (HR, 0.77 [95% CI, 0.61-0.98]). With T-DXd vs T-DM1, 18 pts (6.9%) vs 19 pts (7.2%) were hospitalized; median time to first hospitalization was 219.5 vs 60.0 days, respectively. The improved efficacy and manageable toxicity reported previously for T-DXd, together with this evidence of maintained or improved QoL supports the overall benefit of T-DXd for pts with HER2+ MBC.