Abstract 444P
Background
Human epidermal growth factor receptor 2 (HER2)-low expression, defined as immunohistochemistry (IHC) 1+ or IHC 2+, and in situ hybridization (ISH) negative, in advanced or metastatic gastric cancer (mGC) has been recognized as a new therapeutic biomarker. However, the distinct nature of HER2-low mGC remains controversial. This retrospective study compares clinicopathological features, treatment response, and survival outcomes between HER2-low and HER2-IHC 0 mGC in a real-world setting.
Methods
Data from consecutive patients with HER2-low or HER2-IHC 0 mGC receiving first-line systemic chemotherapy at Queen Mary Hospital, Hong Kong from January 2017 to December 2021 were analyzed. Patient characteristics, HER2 status, metastatic sites, overall response rate (ORR), progression-free survival (PFS), and overall survival (OS) were assessed. Survival analysis was performed using Kaplan-Meier curves, log-rank test, and cox regression.
Results
A total of 229 patients (male: 127, 55.5%; median age: 63, range: 26-86) were included. 137 (59.8%) were classified as HER2-low (HER2 score 1: 113, 49.3%; HER2 score 2: 24, 10.5%) and 92 (40.2%) classified as HER2-IHC 0 mGC. The incidences of liver (HER2-low vs. HER2-IHC 0 23.9% vs. 19.7%, p=0.50), peritoneal (60.9% vs. 67.9%, p=0.52) and distant lymph node metastasis (14.1% vs. 19.8%, p=0.91) were comparable between HER2-low and HER2-IHC 0. The ORR of first-line chemotherapy was 23.1%, with no significant difference between HER2-IHC 0 and HER2-low. Median PFS showed no significant difference (16.5 weeks vs. 19.9 weeks, p=0.19). Similar proportions of patients received second-line treatment (48.9% vs. 48.2%, p=0.93), indicating no significant difference. Median OS did not significantly differ between HER2-IHC 0 and HER2-low tumors (48.6 weeks vs. 56.1 weeks, p=0.52).
Conclusions
Contrary to some studies suggesting HER2-low as a distinct entity, our real-world analysis indicates that HER2-low mGC shares similarities with HER2-IHC 0 in terms of clinical characteristics, chemotherapy response, and prognosis. Further prospective studies focusing on biomarkers and effective treatments for mGC are needed.
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.