Metastatic Breast Cancer ( HER2 Negative)

This study aims to evaluate whether \^68Ga-TROP2 PET/CT, combined with \^18F-FDG PET/CT, can predict the efficacy of anti-TROP2 antibody-drug conjugates in patients with advanced HER2-negative breast cancer. Baseline and dynamic imaging parameters will be used to develop prediction models (primary endpoint: AUC), and their associations with clinical outcomes and tumor TROP2 status will be explored.

The H3RAKLES trial would allow patients with a progressive metastatic breast cancer to have access to one more line of systemic therapy. Patients included in this trial will have already received at least two lines of chemotherapy (and potentially several lines of endocrine therapy for patients with a HR+ disease). In this setting, few treatments have demonstrated a clinically meaningful benefit, and any additional option is valuable. Furthermore, the pre-clinical and clinical rationale indicate a high probability of clinical benefit, as previously shown in Table 1, with all patients treated with trastuzumab and a TKI targeting HER2 displaying a response. Besides, with several years of hindsight for the combination of lapatinib, trastuzumab and capecitabine, we expect excellent tolerance with the same treatment without capecitabine. The H3RAKLES single-arm phase II trial will evaluate the combination of tucatinib, a HER2 TKI, and trastuzumab, a HER2-directed antibody in patients with a HER2-not amplified metastatic or unresectable breast cancer harboring an activating ERBB3 mutation. To demonstrate the actionability of ERBB3 mutations, all patients will receive a combination of trastuzumab and tucatinib, in 3-weeks cycles.

This is an exploratory, ctDNA-guided, multi-stage clinical study designed to evaluate the clinical value of treatment decision-making based on circulating tumor DNA (ctDNA) variant allele frequency (VAF) dynamics in patients with HER2-negative metastatic breast cancer. All enrolled patients will receive antibody-drug conjugate (ADC) therapy for two cycles in Stage 1, with serial ctDNA assessments performed prior to Cycle 1 and Cycle 2. In Stage 2, patients without disease progression will be assigned to different treatment strategies based on the percentage reduction in mean ctDNA VAF. The study aims to assess whether ctDNA VAF dynamics can serve as an early biomarker to guide treatment intensification and improve clinical outcomes in metastatic breast cancer.