Impact of HER2-Low Status in Metastatic Gastric Cancer: A Real-World Retrospective Cohort Study.

Introduction: Information regarding HER2-low tumors in metastatic gastric cancer is sparse. Our aim here was to determine the frequency of low HER2 expression in metastatic gastric cancer and to compare the clinicopathological characteristics, survival, and treatment response of HER2-low patients with HER2-zero patients.

Methods: The clinicopathological features, treatment responses, and survival of HER2-low tumors and HER2-zero tumors were compared.

Results: Of 226 patients, 71 (31.4%) had low HER2 expression and 155 (68.6%) had zero HER2 expression. HER2-low tumors were detected more frequently in older patients and in low-grade tumors than HER2-zero tumors (69% vs. 47.7%, p = 0.003, 16.9% vs. 3.8%, p < 0.001). On the contrary, HER2-zero tumors were more likely to be poor grade than HER2-low tumors (47% vs. 22.2%, p < 0.001). All patients received a first-line chemotherapy regimen. The disease control rate was not statistically different between both groups (40% vs. 46.4%, p = 0.11). The median survival was 12.05 (95% CI, 8.09-16.02) months in HER2-low patients and 10.41 (95% CI, 8.52-12.3) months in HER2-zero patients with no statistical difference (p = 0.73).

Conclusion: HER2-low metastatic gastric cancer has a higher rate of being low grade than HER2-zero tumors. HER2-low metastatic gastric cancer is similar to HER2 zero in terms of chemotherapy response and survival.