Anticipating the Real-World Impact of Therapeutic Innovations in France by Transporting Evidence From the United States (US): A Case Study in Metastatic Triple-Negative Breast Cancer (mTNBC) Based on the Flatiron Health Database

OBJECTIVES: Access to innovative treatments is often earlier in the US than in France, making US data particularly valuable for predicting potential impacts in France and supporting decision-making, including for Health Technology Assessment. Taking the example of mTNBC, this study aims to 1) estimate the overall impact of new therapies on mTNBC management and survival in the US, and 2) anticipate their potential impact in France.

METHODS: This study included female mTNBC patients aged 18+ from the US FlatIron metastatic cohort, diagnosed between 01/07/2013 and 30/09/2023. Patients were categorised into "pre" (≤31/12/2017) and "post" (≥01/04/2019) new therapies cohorts. Study outcomes are changes in treatment used and overall survival (OS). Raw and adjusted analyses were performed to compare the two populations. Propensity score weighting (Moment’s method) was then used to extrapolate US results to the French population, using aggregate data from the French ESME Breast Cancer database.

RESULTS: Among 2126 mTNBC patients, mean age at metastatic diagnosis was 61±13 years, and patients had mainly recurrent disease (64%), ECOG-PS 0 (48%) and metastatic sites in the lung (41%), bone (41%) or lymph nodes (39%). In the pre-new therapies cohort (n=812), taxanes (36%) and platins (25%) were the most commonly used first-line therapies, versus taxanes (44%) and immunotherapies (30%) in the post-new therapies cohort (n=1052). First-line use of anthracyclines decreased from 15% to 7%. Unadjusted OS was higher in the post-new therapies cohort (HR=0.88, p=0.026). Key adjusted results in the US and the expected impact in France will be presented at the conference.

CONCLUSIONS: This study highlights the evolving treatment management of mTNBC and its potential benefit to patient outcomes. As a proof-of-concept study, it illustrates the feasibility of predicting the impact of innovations in France by transporting evidence from the US.