Recent Incidence Trend of Surgically Resected Esophagogastric Junction Adenocarcinoma and Microsatellite Instability Status in Japanese Patients.

BACKGROUND

The incidence trend of esophagogastric junction (EGJ) adenocarcinoma in Japan has not been sufficiently investigated. Little is known about the microsatellite instability (MSI) status of this tumor.

SUMMARY

Previously published studies analyzing the trend of EGJ adenocarcinoma in Japan were reviewed. And a trend of surgically resected cases (Siewert type I-III) utilizing a retrospective multicenter cohort of 379 patients from 4 academic institutions in Japan investigated. Although an increasing trend in the last 2 reports was considered controversial, our cohort demonstrated a growing number of EGJ adenocarcinoma cases between 2006 and 2013. This trend was evident, especially in Siewert type I cases. In the previous 16 studies that performed MSI testing, MSI-high tumors ranged 0-8.3%, though there were no fixed microsatellite markers on EGJ adenocarcinoma. In a recent comprehensive genetic analysis by The Cancer Genome Atlas, MSI testing using the following 7 markers, BAT25, BAT26, BAT40, D2S123, D5S346, D17S250 and TGFR-II showed a favorable correlation with hypermutated tumors. We performed MSI testing using 6 of those markers, except TGFR-II, on 206 cases from one institution, and detected 15 cases (7.3%) with MSI-high. The prevalence of MSI-high was 0% in Siewert type I, 7.6% in type II, and 16.7% in type III. Key message: The number of surgically resected EGJ adenocarcinoma cases gradually increased, and MSI-high was infrequent in Siewert type I-II tumors in our Japanese cohort. Considering MSI-high as a predictive biomarker for emerging immune checkpoint inhibitors, MSI status is becoming more beneficial in EGJ adenocarcinoma.