Health Utilities Associated With Sacituzumab Govitecan (SG) for Treating Unresectable Locally Advanced or Metastatic Triple-Negative Breast Cancer (MTNBC).

OBJECTIVES: SG significantly prolonged progression-free and overall survival vs treatment of physicians’ choice (TPC) for patients with 2L+ mTNBC in ASCENT, a phase 3, randomized, open-label study. We estimated health-state utilities for pre- and post-progression based on EORTC QLQ-C30 measurements to be used in economic evaluations of SG in this aggressive cancer.

METHODS: EORTC QLQ-C30 questionnaires were administered at baseline and day 1 of each treatment cycle and 4 weeks after end-of-treatment/withdrawal visits. Responses were mapped into EQ-5D-3L responses using a published algorithm by Longworth (2014) and weighted by UK tariffs. Mixed-effects repeated measures linear regression (MMRM) were conducted to investigate the effect of disease progression as time-varying covariate. Several patient and disease characteristics possibly impacting utilities were included in an exploratory MMRM analysis. No missing data were imputed.

RESULTS: From 479 patients with minimum one EORTC observation, 411 patients had mapped utility score observations available at baseline and at least one thereafter and were eligible for utility analysis. Multivariate analysis including treatment arm as covariate showed significantly higher utility in the SG arm compared to the chemotherapy (difference of 0.084, 95%CI: 0.016-0.052), and a decrement after disease progression (0.056, 95%CI: 0.042-0.07). Pre-progression utility was 0.710 (95%CI: 0.690-0.730) and 0.626 (95%CI: 0.601-0.651), while post-progression utility was 0.653 (95%CI: 0.631-0.676) and 0.569 (95%CI: 0.543-0.596) in SG vs TPC, respectively. Results remained similar irrespective of mapping methods and statistical modelling approach. Plausibility of such large difference and a carry-over impact was confirmed by practicing UK clinicians as it aligns with large responses seen in the trial. Limitations include large amounts of missing data post 6 months – however, this is expected and correlates with progression.

CONCLUSIONS: Treatment with SG provides large utility gains vs TPC in late line mTNBC, that is carried over and preserved after progression.