Primary trastuzumab-resistance after (neo)adjuvant trastuzumab-containing treatment for HER2-positive breast cancer patients in real-world practice

Abstract Background It is difficult to define primary trastuzumab-resistant patients (PTR) after (neo)adjuvant trastuzumab with minimal data and understanding of the actual prevalence, prognosis, and potential treatment strategies in real-world setting. Patients and methods Medical records of 1096 HER2-positive early stage breast cancer patients who had received (neo)adjuvant trastuzumab-containing treatment during 2010 to 2016 in Cancer hospital & Chinese Academy of Medical Sciences were reviewed. PTR was defined as recurrence during adjuvant trastuzumab or within 12 months from their last (neo)adjuvant trastuzumab dispensing. The cut-off date for data collection was 1 September, 2018, with a median follow-up time of 46 months. Results A total of 126 recurrences were observed, and 75 of them (6.8%, 75/1096) were categorized as PTR, the remaining were non-PTR. The prognosis of patients in PTR group was much inferior to non-PTR group (27 months vs. not reached, P Conclusion This study verified the rationality of present definition of PTR after (neo)adjuvant trastuzumab. PTR did have a poor prognosis. Further research and clinical trials are required to establish best treatment patterns for these patients.