Aranzazu Fernandez-Martinez, Barbara Adamo, Blanca Gonzalez-Farre, Lisa A. Carey, Francesco Schettini, Benedetta Conte, Charles M. Perou, Jamunarani Veeraraghavan, Jan C. Brase, Sabino De Placido, Tomás Pascual, Mariavittoria Locci, Pierfranco Conte, Patricia Villagrasa, Montserrat Muñoz, Sonia Pernas, Fara Brasó-Maristany, Olga Martínez, Patricia Galván, Maria Vidal, Mothaffar F. Rimawi, C. Kent Osborne, Carla Rognoni, Gaia Griguolo, Rachel Schiff, Nuria Chic, Valentina Guarneri, Aleix Prat, Schettini, F., Pascual, T., Conte, B., Chic, N., Braso-Maristany, F., Galvan, P., Martinez, O., Adamo, B., Vidal, M., Munoz, M., Fernandez-Martinez, A., Rognoni, C., Griguolo, G., Guarneri, V., Conte, P. F., Locci, M., Brase, J. C., Gonzalez-Farre, B., Villagrasa, P., De Placido, S., Schiff, R., Veeraraghavan, J., Rimawi, M. F., Osborne, C. K., Pernas, S., Perou, C. M., Carey, L. A., and Prat, A.
Background: HER2-positive (HER2+) breast cancer (BC) comprises all the four PAM50 molecular subtypes. Among these, the HER2-Enriched (HER2-E) appear to be associated with higher pathological complete response (pCR) rates following anti-HER2-based regimens. Here, we present a meta-analysis to validate the association of the HER2-E subtype with pCR following anti-HER2-based neoadjuvant treatments with or without chemotherapy (CT). Methods: A systematic literature search was performed in February 2019. The primary objective was to compare the association between HER2-E subtype (versus others) and pCR. Selected secondary objectives were to compare the association between 1) HER2-E subtype and pCR in CT-free studies, 2) HER2-E subtype within hormone receptor (HR)-negative and HR+ disease and 3) HR-negative disease (versus HR+) and pCR in all patients and within HER2-E subtype. A random-effect model was applied. The Higgins��� I2 was used to quantify heterogeneity. Results: Sixteen studies were included, 5 of which tested CT-free regimens. HER2-E subtype was significantly associated with pCR in all patients (odds ratio [OR] = 3.50, p < 0.001, I2 = 33%), in HR+ (OR = 3.61, p < 0.001, I2 = 1%) and HR-negative tumors (OR = 2.28, p = 0.01, I2 = 47%). In CT-free studies, HER2-E subtype was associated with pCR in all patients (OR = 5.52, p < 0.001, I2 = 0%) and in HR + disease (OR = 4.08, p = 0.001, I2 = 0%). HR-negative status was significantly associated with pCR compared to HR + status in all patients (OR = 2.41, p < 0.001, I2 = 30%) and within the HER2-E subtype (OR = 1.76, p < 0.001, I2 = 0%). Conclusions: The HER2-E biomarker identifies patients with a higher likelihood of achieving a pCR following neoadjuvant anti-HER2-based therapy beyond HR status and CT use. Future trial designs to escalate or de-escalate systemic therapy in HER2+ disease should consider this genomic biomarker.