Huayan Gu,1,* Teng Zhu,2,* JiaLing Ding,1 Zhi Yang,1 Shuangyi Qi,1 Guilong Guo1 

1Department of Breast Surgery, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, People’s Republic of China; 2Department of Gastrointestinal Surgery, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, People’s Republic of China

*These authors contributed equally to this work

Correspondence: Guilong Guo, Department of Breast Surgery, The First Affiliated Hospital of Wenzhou Medical University, Nanbaixiang Street, Wenzhou City, Zhejiang Province, People’s Republic of China, Email guoguilong@sina.com

Purpose: This study efforts to explore the association of adverse events (AEs) with efficacy in HER2-positive breast cancer patients treated with TDM1.
Methods and Materials: This retrospective study included women diagnosed with HER2+ BC treated with TDM1 from January 2012 to December 2023. Event-free survival (EFS) was the endpoint. Tumour response was assessed by disease control rate (DCR) and objective response rate (ORR). The chi-squared test, analysis of variance (ANOVA), Cox proportional hazards regression and Kaplan-Meier survival analysis was employed to evaluate the association of AEs with tumour efficacy.
Results: A total of 48 women with a median age of 52 years (median follow-up 8.4 months) were included in the study. Among them, 33 patients (68.8%) experienced adverse events, including platelet depletion and liver function abnormalities, 3 patients (6.3%) discontinued TDM1 due to severe platelet depletion. The overall objective response rate (ORR) was 25.0% and the disease control rate (DCR) was 43.8%. Using the Chi-squared test, we found a statistically significant difference in ORR and DCR between patients who developed a platelet reduction and those who did not. DCR was significantly higher in patients with liver dysfunction than in those without. ANOVA showed that exposure to hepatic dysfunction and platelet reduction, lines of therapy, and treatment course were associated with EFS. In the Kaplan-Meier survival analysis, both liver dysfunction and platelet reduction were correlated with significantly longer EFS (p=0.033 and p=0.038, respectively).
Conclusion: This retrospective study demonstrated that AEs were associated with tumour efficacy in patients with HER2+ BC treated with TDM1.

Keywords: HER2-positive breast cancer, adverse events, T-DM1, tumour efficacy