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In Japan, with the increasing prevalence of gastroesophageal reflux disease (GERD) and growing public interest, the Japanese Society of Gastroenterology issued Evidence-based Clinical Practice Guidelines for GERD (1st edition) in 2009 and a revised 2nd edition in 2015. A number of studies on GERD were subsequently conducted in Japan and abroad, and vonoprazan, a potassium-competitive acid blocker (P-CAB), became available for the first time in Japan in February 2015. The revised 3rd edition (Japanese edition), which incorporates new findings and information, was published in April 2021. These guidelines are summarized herein, particularly sections related to the treatment of GERD. The important clinical issues addressed in the present revision are (i) the introduction of treatment algorithms that classify GERD into reflux esophagitis and non-erosive reflux disease, (ii) the clarification of treatment algorithms based on to the severity of reflux esophagitis, and (iii) the positioning of vonoprazan in the treatment for GERD. The present guidelines propose vonoprazan as the initial/maintenance treatment for severe reflux esophagitis. They also recommend vonoprazan or PPI as an initial treatment for mild reflux esophagitis and recommended PPI and proposed vonoprazan as maintenance treatment. These updated guidelines offer the best clinical strategies for GERD patients in Japan and hope that they will be of global use for the diagnosis and treatment for GERD.

Background: Vonoprazan (VPZ) is a novel potassium-competitive acid blocker that may be clinically beneficial for proton pump inhibitor (PPI)-resistant reflux esophagitis (RE). The aim of this study was to investigate the efficacies of VPZ therapy at 20 mg for 4 weeks in patients with PPI-resistant RE and VPZ maintenance therapy at 10 mg for 8 weeks in patients who have been successfully treated. Methods: Subjects comprised 24 patients with PPI-resistant RE (Los Angeles classification grade A/B/C/D: 3/7/11/3). After confirming PPI-resistant RE by endoscopy, 20 mg VPZ was administered. Endoscopy was performed 4 weeks after the initiation of VPZ. Symptoms were evaluated using the frequency scale for the symptoms of gastroesophageal reflux disease (FSSG). Maintenance therapy with 10 mg VPZ was performed and endoscopy was conducted after 8 weeks. Results: In 21 (87.5%) out of 24 patients, esophageal mucosal breaks were successfully treated by 20 mg VPZ. The median FSSG score was significantly lower on days 1-7, 14, and 28 after the initiation of VPZ than before its administration. Maintenance therapy with 10 mg VPZ prevented the relapse of esophageal mucosal breaks in 16 (76.2%) out of 21 patients. Conclusion: VPZ was effective for most patients with PPI-resistant RE.

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Abstract. The genomic region containing PIK3CA was found to be amplified in esophageal squamous cell carcinoma (ESCC) tissue. PIK3CA at 3q26, which encodes the p110· catalytic subunit of phosphatidylinositol (PI) 3-kinase, is a unique intracellular signal transducer characterized by its lipid substrate specificity. In order to characterize PIK3CA in ESCC, we investigated hot-spot mutations in exons 1, 9 and 20, the copy number gain, the expression levels of mRNA and protein. Analysis in exon 9 of the PIK3CA gene revealed mutation in 7.7% (4 of 52) of ESCC samples. No mutation was detected in either exon 1 or exon 20. Copy number amplifications of PIK3CA were found in 12 of the 45 patients (26.7%). PIK3CA mRNAs were examined in 37 ESCC patients as determined by quantitative RT-PCR and the mean mRNA level of PIK3CA in ESCC tissues was 2.61-fold higher compared with that in corresponding non-tumorous esophageal epithelia (P<0.001). Immunohistochemically, positive immunoreaction for PIK3CA was detectable in 33 of 66 (50.0%) ESCC cases, while it was not detectable in the remaining 33 cases. Furthermore, comparing the cases with negative staining with those with positive staining for PIK3CA, the presence of node metastasis was significantly correlated with those with positive staining (P<0.05). This study is the first report providing comprehensive analysis of PIK3CA expression in ESCC. These results indicate that PIK3CA may play a crucial role in the development of ESCC and serve as an indicator for lymph node metastasis.