Abstract P5-02-40: Anthracycline improves the outcome of neoadjuvant trastuzumab-treated breast cancer patients with FcγRIIIA F/F genotype by decreasing the ratios of CD8+PD1+ and CD68+PDL1+ cells
Authors: Lee Kaping , Luo Rongzhen , Lu Qianyi , Wang Shusen , Xu Fei 
Published: March 2023

Abstract
Background: Antibody-dependent cell-mediated cytotoxicity (ADCC) is one of the most important mechanisms of trastuzumab. Fragment C Gamma receptor (FcγR) IIA and IIIA polymorphisms influence the affinity of immunoglobin G (IgG). Recently, FcγRIIA and FcγRIIIA polymorphisms have identified with the efficacy of trastuzumab. However, whether FcγR polymorphisms are associated with the efficacy of trastuzumab in the neoadjuvant setting was unclear.
Patients and methods: We retrospectively enrolled 101 patients with HER2-positive breast cancer receiving chemotherapy plus trastuzumab at least four cycles as neoadjuvant therapy and mastectomy in Sun Yat-sen university cancer center from May 2015 to March 2021. Among them, twenty patients were excluded because lacking of blood samples. Polymorphisms of FcγRIIA(rs1801274) and FcγRIIIA(rs396991) were examined by nested polymerase chain reaction (PCR) and sanger sequencing. Lastly, we performed multiple immunohistochemistry (mIHC) to examine the expressions of CD8, CD68, CD57, PD1 and PDL1.
Results: Blood samples (n=81) were successfully detected. No significant differences between FcγRIIA/FcγRIIIA genotypes and clinical characteristics, including age, clinical stages, menstrual status, molecular subtyping, treatment and pathological complete response (pCR) rate. In paclitaxel-based treatment subgroup (n=34), FcγRIIIA polymorphism was significantly correlated with pCR rate (P&lt; 0.05,Table1), moreover, the disease-free survivals (DFS) in FcγRIIIA-158V carriers subgroup (high affinity) were significantly longer than that in FcγRIIIA-158 F/F genotype group (low affinity) (P=0.036), while that was not significant difference in patients with anthracycline-based treatment (n=47, P=0.248), indicating that anthracycline enhanced the efficacy of neoadjuvant therapy in patients with FcγRIIIA F/F genotype(low affinity). So far, there is no recurrence events in paclitaxel-based treatment group with FcγRIIIA-158V carriers genotype. The mIHC showed that the ratios of stroma CD8+PD1+ and CD68+PDL1+ cells were significantly higher in anthracycline-based treatment group (Table 2), respectively, indicating that anthracycline improved the efficacy of neoadjuvant targeted therapy by decreasing the ratios of exhausted immune cells.
Conclusions: FcγRIIIA-158V genotype is associated with better outcome in HER2-positive breast cancer patients who received paclitaxel combined with trastuzumab as neoadjuvant therapy. Anthracycline improves the outcome of neoadjuvant trastuzumab-treated breast cancer patients with FcγRIIIA F/F genotype by decreasing the ratios of CD8+PD1+ and CD68+PDL1+ cells.
Correlation between FcγRIIIA and pCR Correlation between FcγRIIIA and pCR in total population and paclitaxel-based treatment population.
Ratios of immune cells Ratios of immune cells in anthracycline-based and paclitaxel-based treatment group.
Citation Format: Kaping Lee, Rongzhen Luo, Qianyi Lu, Shusen Wang, Fei Xu. Anthracycline improves the outcome of neoadjuvant trastuzumab-treated breast cancer patients with FcγRIIIA F/F genotype by decreasing the ratios of CD8+PD1+ and CD68+PDL1+ cells [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-02-40.