A Study to Investigate the Prevalence of Human Epidermal Growth Factor Receptor 2 (HER2) Immunohistochemistry (IHC) 3+ and Characterize the Clinicopathologic Features of Gynecologic Cancers in Taiwan

Trastuzumab Deruxtecan (T-DXd) is a humanized anti-HER2 monoclonal antibody covalently linked to DXd, which is a topoisomerase 1 inhibitor. T-DXd has been approved for the treatment of HER2-positive breast cancer, HER2-mutated lung cancer, HER2-positive gastric cancer, and HER2-low breast cancer in Taiwan. Aside from clinical benefits in the above cancers, the DESTINY-PanTumor02 (NCT04482309) Phase II trial showed that T-DXd continued to demonstrate clinically meaningful and durable responses and survival benefits in previously treated patients across multiple HER2-expressing advanced solid tumors. Among multiple types of solid tumors in the DESTINY-PanTumor02 trial, T-DXd showed a high confirmed objective response rate in heavily treated HER2 IHC 3+ endometrial cancer (EC, 84.6%, 11/13), ovarian cancer (OC, 63.6%, 7/11), and cervical cancer (CC, 75%, 6/8). Previous evidence showed that HER2-expressing gynecologic cancers have limited treatment options and have poor prognoses under standard therapies. Data from DESTINY-PanTumor02 therefore serve as supporting evidence for T-DXd to become a potential therapeutic option for these HER2-expressing gynecologic cancers. In August 2023, T-DXd received the FDA-designated breakthrough therapy designations and was approved in April 2024 for treating unresectable and metastatic HER2 IHC 3+ solid tumors that have progressed after prior treatment or lack satisfactory alternative options. The National Comprehensive Cancer Network (NCCN) has included T-DXd as a treatment option for HER2-positive endometrial, ovarian, and cervical carcinomas in their guidelines as of V1 2024. However, the prevalence rate of HER2 IHC 3+ in recurrent advanced endometrial, ovarian, and cervical cancers in Taiwan remains unclear. Limited information is available regarding the HER2 amplification rate by ISH for specific cancer types. In this retrospective, non-interventional study, the investigators aim to explore the prevalence of HER2 IHC 3+ in r