Immunoglobulin G Fragment C Receptor Polymorphisms and Clinical Efficacy of Trastuzumab-Based Therapy in Patients With HER-2/ neu –Positive Metastatic Breast Cancer

Our population was in Hardy-Weinberg equilibrium except for the Fc gamma RIIb polymorphism. The Fc gamma RIIIa-158 V/V genotype was significantly correlated with objective response rate (ORR) and progression-free survival (PFS). Also, there was trend significance in ORR and PFS for the Fc gamma RIIa-131 H/H genotype. The combination of the two favorable genotypes (VV and/or H/H) was independently associated with better ORR and PFS compared with the other combinations. The ADCC analysis showed that V/V and/or H/H PBMCs had a significantly higher trastuzumab-mediated cytotoxicity than PBMCs harboring different genotypes.

These data support for the first time the hypothesis that Fc gamma R-mediated ADCC plays an important role in the clinical effect of trastuzumab. Prospective studies are needed to confirm the role of Fc gamma R polymorphisms in predicting clinical outcome of patients with breast cancer treated with trastuzumab-based therapy.