AUTHOR=Hu Ye , Chen Fengxi , Sun Siwen , Xv Lingzhi , Wang Xueqing , Wang Meiling , Zhao Shanshan , Zhao Zuowei , Li Man TITLE=mTOR inhibitor introduce disitamab vedotin (RC48-ADC) rechallenge microtubule-chemotherapy resistance in HER2-low MBC patients with PI3K mutation JOURNAL=Frontiers in Oncology VOLUME=14 YEAR=2024 URL=https://www.frontiersin.org/journals/oncology/articles/10.3389/fonc.2024.1312634 DOI=10.3389/fonc.2024.1312634 ISSN=2234-943X ABSTRACT=

This study aimed to explore the efficacy and potential mechanisms of rechallenge therapy with microtubule-targeting agents (MTAs) in patients with HER2-low metastatic breast cancer (MBC). We performed a systematic review to investigate the rechallenge treatment concept in the field of HER2-low MBC treatment and utilized a series of cases identified in the literature to illustrate the concept. Here we reported two clinical cases of HER2-low MBC patients whose disease progressed after prior treatment with MTAs such as docetaxel and vincristine. When rechallenged with disitamab vedotin ((RC48-antibody-drug conjugate (ADC), a monomethyl auristatin (MMAE) MTA)), both patients achieved a partial response and the final progression-free survival (PFS) was 13.5 and 9 months, respectively. Genomic profiling detected a PIK3CA H1047R mutation in the patients. The patients were treated with everolimus before being rechallenged with RC48, which may lead to a better response. This study further summarizes and analyzes the potential mechanism of the PI3K-AKT signaling pathway in MTA resistance and reveals that the PIK3CA H1047R mutation may be a potential molecular marker for the efficacy prediction of mTOR inhibitors, providing new insights and potential therapeutic strategies for the application of MTAs to MBC patients.