Real-world effectiveness of post-trastuzumab emtansine treatment for human epidermal growth factor receptor 2-positive metastatic breast cancer: a multicenter, matched cohort analysis from the Epidemiology Strategy and Medical Economics database (2008-2018)

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Background: Real-world data (RWD) can contextualize clinical trial data. We present real-world evidence thatsupplemented the single-arm DESTINY-Breast01 trial, which assessed the efficacy and safety of trastuzumabderuxtecan (T-DXd) in patients with human epidermal growth factor receptor 2-positive (HER2þ) metastatic breastcancer (mBC) previously treated with trastuzumab emtansine (T-DM1).Patients and methods: Patients from the French Epidemiology Strategy and Medical Economics (ESME) mBC databasewho initiated treatment for HER2þ mBC between 1 January 2008 and 31 December 2016, and received one or moretreatment lines following T-DM1 were propensity score matched 1 : 1 to patients from DESTINY-Breast01 to create anESME DB-01 matched cohort. Treatment patterns, real-world best overall response, real-world objective response rate(rwORR), real-world disease control rate (rwDCR), real-world progression-free survival (rwPFS), and overall survival (OS)were estimated, including by prior pertuzumab exposure and de novo/relapsed mBC status.Results: A total of 137 patients from the ESME mBC database (78 received prior pertuzumab, 59 did not) were matchedto 137 patients from DESTINY-Breast01. In the ESME DB-01 matched cohort, 73.7% received an anti-HER2 drug afterT-DM1 treatment. The rwORR was 12.2% (95% confidence interval [CI] 6.2% to 18.2%; only partial responses) andrwDCR was 73.9% (95% CI 65.9% to 81.9%). The median rwPFS was 4.7 months (95% CI 3.8-6.0 months) and similarregardless of prior pertuzumab exposure or de novo/relapsed mBC status. The median OS was 24.1 months (95% CI18.5-26.4 months) and longer in patients naive to versus exposed to pertuzumab and in patients with de novoversus relapsed mBC.Conclusion: These RWD contextualized results of DESTINY-Breast01 and demonstrated an unmet medical need inpatients with HER2þ mBC after T-DM1 treatment

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