Patritumab deruxtecan in untreated hormone receptor-positive/HER2-negative early breast cancer: final results from part A of the window-of-opportunity SOLTI TOT-HER3 pre-operative study.

BACKGROUND: Patritumab deruxtecan (HER3-DXd) is a human epidermal growth factor receptor 3 (HER3)-directed antibody-drug conjugate composed of a fully human anti-HER3 monoclonal antibody (patritumab) covalently linked to a topoisomerase I inhibitor payload via a stable, tumor-selective, tetrapeptide-based cleavable linker. TOT-HER3 is a window-of-opportunity study designed to assess the biological activity, measured by CelTIL score [= -0.8 × tumor cellularity (in %)  + 1.3  × tumor-infiltrating lymphocytes (TILs) (in %)], and clinical activity of HER3-DXd during short-term (21 days) pre-operative treatment in patients with primary operable HER2-negative early breast cancer. PATIENTS AND METHODS: Patients with previously untreated hormone receptor-positive/HER2-negative tumors were allocated to one of four cohorts according to baseline ERBB3 messenger RNA expression. All patients received one dose of HER3-DXd 6.4 mg/kg. The primary objective was to evaluate change from baseline in CelTIL score. RESULTS: Seventy-seven patients were evaluated for efficacy. A significant change in CelTIL score was observed, with a median increase from baseline of 3.5 (interquartile range, -3.8 to 12.7; P = 0.003). Among patients assessable for clinical response (n = 62), an overall response rate of 45% was observed (tumor measurement by caliper), with a trend toward an increase in CelTIL score among responders compared with non-responders (mean difference, +11.9 versus +1.9). Change in CelTIL score was independent of baseline ERBB3 messenger RNA and HER3 protein levels. Genomic changes occurred, including switching toward a less proliferative tumor phenotype based on PAM50 subtypes, suppression of cell proliferation genes, and induction of genes associated with immunity. Treatment-emergent adverse events were observed in 96% of patients (14% grade ≥3); most common were nausea, fatigue, alopecia, diarrhea, vomiting, abdominal pain, and neutrophil count decrease. CONCLUSIONS: A single dose of HER3-DXd was associated with clinical response, increased immune infiltration, suppression of proliferation in hormone receptor-positive/HER2-negative early breast cancer, and a tolerable safety profile consistent with previously reported results. These findings support further study of HER3-DXd in early breast cancer.

Prognostic value of Ki-67 according to age in patients with triple-negative breast cancer.

PURPOSE: The prognostic value of Ki-67 in triple-negative breast cancer (TNBC) is yet unclear because the cut-off points employed differ widely and its predictive effect may vary according to age. The purpose of this study was to analyze the role of Ki-67 among patients with TNBC, and determine the optimal Ki-67 cut-off point to demonstrate its prognostic relevance associated with patient age and treatment strategy. METHODS/PATIENTS: 201 consecutive patients treated for primary TNBC from 1999 to 2014 were analyzed. Clinicopathological characteristics and outcomes were compared between patients treated with neoadjuvant or adjuvant chemotherapy. We used time-dependent receiver operating characteristic (ROC) curve and time-dependent area under the ROC curve (AUC) to evaluate the discriminative ability of Ki-67 at 3 and 5 years of follow-up. A Ki-67 cut-off point that maximized sensibility and specificity was established. Interaction effect between age and Ki-67 on disease-free survival (DFS) and overall survival (OS) was evaluated by stratified analysis. RESULTS: According to the coordinates of the ROC curves, the best cut-off point for Ki-67 was 60% (high/low). In the whole group, there was not a statistically significant association between Ki-67 and OS and DFS, using a cut-off point of 60%. In multivariate analysis (COX proportional hazards regression), for DFS high Ki-67 (> 60%) was a poor prognostic factor in patients > 40 years old and a better prognostic factor among the patients < 40 years old. CONCLUSION: Prognostic value of Ki-67 in TNBC, using a cut-off point of 60%, may vary depending on age.