03-02-2025 | Breast Cancer | Research
Pathologic complete response rates of patients with ER-low/HER2-negative breast cancer treated with neoadjuvant pembrolizumab plus chemotherapy in the neo-real study
Authors:
Renata Colombo Bonadio, Monique Celeste Tavares, Flávia Cavalcanti Balint, Isadora Martins de Sousa, Ana Carolina Marin Comini, Fernanda Madasi, Jose Bines, Rafael Dal Ponte Ferreira, Daniela Dornelles Rosa, Candice Lima Santos, Zenaide Silva de Souza, Daniele Assad-Suzuki, Júlio Antônio Pereira de Araújo, Débora de Melo Gagliato, Carlos Henrique dos Anjos, Bruna M. Zucchetti, Anezka Ferrari, Mayana Lopes de Brito, Renata Cangussu, Maria Marcela Fernandes Monteiro, Paulo M. Hoff, Laura Testa, Maria del Pilar Estevez-Diz, Romualdo Barroso-Sousa
Published in:
Breast Cancer Research and Treatment
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Abstract
Purpose
Estrogen receptor-low (ER-low) breast cancer (BC) present clinicopathological features and disease behavior resembling triple-negative breast cancer, but have been frequently excluded from pivotal trials designed for the latter. Since neoadjuvant pembrolizumab plus chemotherapy (P + CT) is the new standard of care for stage II-III triple-negative breast cancer (TNBC), we aimed to access the effectiveness of this therapy for ER-low tumors.
Methods
We evaluated patients with ER-low BC included in the Neo-Real/ GBECAM-0123 study, a real-world data study evaluating patients treated with neoadjuvant P + CT since July 2020 across ten cancer centers. The objective of this study was to evaluate the effectiveness of neoadjuvant P + CT through pathologic complete response (pCR).
Results
Twenty patients were included in this analysis. Median age was 40 years (range 28–64). Most patients had grade 3 tumors (n = 18, 90%), with a median Ki67 index of 75% (range 30–95%), and 70% had stage II tumors.
All the twenty patients were submitted to surgery, with a pCR observed in 12 cases (pCR rate of 60%). Receiving less than 6 cycles of pembrolizumab was associated with a trend towards worse pCR rates (20% vs 73.3%).
Conclusions
The clinicopathological features and the response to neoadjuvant P + CT observed in this ER-low BC cohort are similar to that observed in TNBC. Patients with stage II-III ER-low/HER2- BC should be treated with neoadjuvant P + CT following the treatment standards for TNBC, and proper adherence to the regimen is relevant to improve effectiveness.