Prevalence and clinicopathological features of microsatellite instability-high metastatic or recurrent gastric and esophagogastric junction cancer: WJOG13320GPS

• Published in: Gastric cancer : official journal of the International Gastric Cancer Association and the Japanese Gastric Cancer Association 2024-12
• Main Authors: Komori, Azusa, Hironaka, Shuichi, Kadowaki, Shigenori, Mitani, Seiichiro, Furuta, Mitsuhiro, Kawakami, Takeshi, Makiyama, Akitaka, Takegawa, Naoki, Sugiyama, Keiji, Hirano, Hidekazu, Ando, Takayuki, Matsushima, Tomohiro, Chida, Akihiko, Kashiwada, Tomomi, Komoda, Masato, Matsumoto, Toshihiko, Oda, Hisanobu, Yabusaki, Hiroshi, Kawakami, Hisato, Yamazaki, Kentaro, Boku, Narikazu, Hyodo, Ichinosuke, Yoshimura, Kenichi, Muro, Kei
• Format: Article
• Language: English
• ISSN: 1436-3291; 1436-3305; 1436-3305
• DOI: 10.1007/s10120-024-01579-2

Microsatellite instability (MSI)-high tumors represent a distinct, small-fraction subtype in esophagogastric junction cancer or gastric cancer (GC), yet their clinical significance remains poorly understood. This study aimed to investigate the prevalence and clinicopathological features of chemotherapy-naïve metastatic or recurrent MSI-high GC as a prescreening study for a phase II trial of nivolumab plus ipilimumab. Key inclusion criteria included metastatic or recurrent adenocarcinoma of GC, ECOG performance status of 0 or 1, and no prior systemic therapy for metastatic or recurrent disease. MSI status was tested using multiplex PCR fragment analysis (MSI Testing Kit, FALCO). The primary endpoint was the prevalence of MSI-high GC. Between October 2020 and October 2022, 930 eligible patients from 75 centers in Japan were analyzed. The prevalence of MSI-high GC was 5.6% (95% CI 4.2-7.3). MSI-high GC was more frequently observed in females than males (9.6% vs 3.8%, p