Trastuzumab Resistance in Patients With HER2-Positive Advanced Breast Cancer: Results From the SONABRE Registry.

BACKGROUND: This study aims to explore whether first-line pertuzumab use modifies the effect of prior use of (neo-) adjuvant trastuzumab on the PFS of first-line HER2-targeted therapy in patients with human epidermal growth factor receptor 2 (HER2)-positive advanced breast cancer (ABC). METHODS: Patients diagnosed with HER2-positive ABC in 2008 to 2018 in 9 Dutch hospitals were derived from the SONABRE Registry (NCT03577197). Patients diagnosed with de novo metastatic breast cancer were excluded. Patients receiving first-line trastuzumab-based therapy for ABC were selected and divided into trastuzumab naïve (n = 113) and trastuzumab pretreated (n = 112). Progression-free survival (PFS) was compared using multivariable Cox proportional hazard models. The interaction effect of first-line pertuzumab was tested using the likelihood-ratio test. RESULTS: The median follow-up time was 47 months (95% confidence interval [CI]: 42-52). When comparing trastuzumab pretreated with trastuzumab naïve patients, the hazard ratio for first-line progression was 2.07 (CI:1.47-2.92). For trastuzumab pretreated patients who received first-line trastuzumab without pertuzumab, the hazard ratio for progression was 2.60 (95% CI:1.72-3.93), whereas for those who received first-line trastuzumab with pertuzumab the hazard ratio was 1.43 (95% CI: 0.81-2.52) (P interaction = .10). CONCLUSIONS: Prior use of trastuzumab as (neo-)adjuvant treatment had a negative impact on PFS of first-line HER2-targeted therapy outcomes. Adding pertuzumab to first-line trastuzumab-based therapy decreased the negative impact of prior (neo-)adjuvant trastuzumab use on first-line PFS. Further studies are needed to assess the effect of prior (neo-)adjuvant pertuzumab use on the outcomes of first-line pertuzumab-based therapy.

Real-world time trends in overall survival, treatments and patient characteristics in HR+/HER2- metastatic breast cancer: an observational study of the SONABRE Registry.

Background: This study aims to evaluate whether changes in therapeutic strategies have improved survival of patients diagnosed with hormone receptor positive (HR+), HER2 negative (HER2-) advanced breast cancer (ABC) in real-world. Methods: All 1950 patients systemically treated for HR+/HER2- ABC and diagnosed between 2008 and 2019 in eight hospitals were retrieved from the SONABRE Registry (NCT-03577197). Patients were categorized per three-year cohorts based on year of ABC diagnosis. Tests for trend were used to examine differences in baseline characteristics, Kaplan-Meier methods and Cox proportional hazards for survival analyses, and competing-risk methods for 3-year use of systemic therapy. Findings: Over time, patients were older (≥70 years, 37%, n = 169/456 in 2008-2010, 47%, n = 233/493 in 2017-2019, p = 0.004) and more often had multiple metastatic sites at ABC diagnosis (48%, n = 220/456 in 2008-2010, 56%, n = 275/493 in 2017-2019, p = 0.002). Among patients with metachronous metastases the prior exposure to (neo-) adjuvant therapies increased over time (chemotherapy, 38%, n = 138/362 in 2008-2010, 48%, n = 181/376 in 2017-2019, p = <0.001; endocrine therapy, 64%, n = 231/362 in 2008-2010, 72%, n = 271/376 in 2017-2019, p = <0.001). Overall survival significantly improved from median 31.1 months (95% CI:28.2-34.3) for patients diagnosed in 2008-2010 to 38.4 months (95% CI:34.0-41.1) in 2017-2019 (adjusted hazard ratio = 0.76, 95% CI:0.64-0.90; p = 0.001). Three-year use of CDK4/6 inhibitors increased from 0% for patients diagnosed in 2008-2010 to 54% for diagnosis in 2017-2019. Conversely, three-year use of chemotherapy was 50% versus 36%, respectively. Interpretation: Over time, patients diagnosed with HR+/HER2- ABC presented with less favourable patient characteristics. Nevertheless, we observed that overall survival of ABC increased between 2008 and 2019, with increased use of endocrine/targeted therapies. Funding: The SONABRE Registry is supported by the Netherlands Organization for Health Research and Development (ZonMw: 80-82500-98-8003); Novartis BV; Roche; Pfizer; and Eli Lilly & Co. Funding sources had no role in the writing of the manuscript.