大澤 英之

BACKGROUND: Neoadjuvant therapy has been increasingly adopted for resectable pancreatic ductal adenocarcinoma (PDAC) in Japan following the Prep-02/JSAP-05 trial. However, real-world evidence regarding effectiveness and underlying pathological mechanisms remains limited. This retrospective study evaluated neoadjuvant chemotherapy with gemcitabine plus S-1 (NAC-GS) impacts on resectable PDAC patient oncological and pathological outcomes. METHODS: Consecutive resectable PDAC patients treated with NAC-GS (n = 60) or upfront surgery (UFS) (n = 101) between 2013 and 2023 were retrospectively analyzed (total diagnosed during the study period, n = 186). An intention-to-treat principle assessed overall survival (OS) and recurrence-free survival (RFS). Propensity score matching using six baseline variables (1:1) minimized selection bias. RESULTS: Fifty-four patients were included in each group. The NAC-GS group demonstrated significantly longer OS than the UFS group (hazard ratio [HR], 0.48; 95% confidence interval [CI], 0.25-0.90; P = 0.023). Among resected cases, NAC-GS was associated with improved OS (HR, 0.42; 95% CI, 0.20-0.90; P = 0.026). Pathologically, the NAC-GS group showed significantly lower lymph node stage and less lymphatic invasion. Pathological complete response was observed in 4.0% of NAC-GS patients. DISCUSSION: Neoadjuvant chemotherapy with GS was associated with prolonged survival in resectable PDAC, potentially through lymphatic spread suppression. Pathological complete response was rare but may represent a clinically meaningful benefit of neoadjuvant treatment in selected patients.

BACKGROUND AND PURPOSE: The peritoneal cavity constitutes a unique immune microenvironment that critically influences the pathobiology of peritoneal metastasis (PM). This study aimed to clarify the mechanisms by which local immune alterations affect the efficacy of intraperitoneal (IP) chemotherapy for PM from gastric cancer (GC). METHOD: Peritoneal lavage or ascitic fluid was obtained from 42 patients with GC and PM treated with IP paclitaxel (PTX) in combination with systemic oxaliplatin and oral S-1. Serial samples from 31 patients were analyzed after 1-3 cycles of chemotherapy. Immune cell subsets were evaluated using multicolor flow cytometry with monoclonal antibodies, and the functional properties of peritoneal eosinophils were assessed using gene expression profiling and cytotoxicity assays. RESULTS: IP chemotherapy was associated with decreased CD4(+) T cells and increased CD11b(+) myeloid cells. Notably, many patients, particularly those with negative cytology (CY0), exhibited striking recruitment of CD66b(+) CD16(-) CD193(+) Siglec-F(+) eosinophils into the peritoneal cavity. Eosinophil expansion was correlated with improved clinical outcomes. Post-treatment eosinophils displayed an activated, partially degranulated phenotype with elevated CD11b and CD63 expression and distinct messenger RNA signatures compared with circulating eosinophils. Peritoneal eosinophils demonstrated the ability to induce apoptosis in GC cells. CONCLUSION: IP PTX promotes the recruitment and activation of eosinophils with potent antitumor activity in the peritoneal cavity. Early post-treatment abdominal eosinophilia is a robust prognostic biomarker and may represent a promising therapeutic target to enhance the efficacy of IP chemotherapy in patients with PM from GC.

Introduction: Peritoneal metastasis (PM) is the most common site of recurrence following curative resection for advanced gastric cancer (GC). Along with disease progression, it can lead to complications such as intestinal obstruction, hydronephrosis, obstructive jaundice, and ascites, significantly impairing the patient’s quality of life. Therefore, peritoneal metastasis is considered a critical target for treatment. In general, these patients are treated with systemic chemotherapy; however, the therapeutic effect is often limited due to the anticancer agents’ poor penetration into the peritoneal cavity. We aim to identify factors associated with the best overall survival (OS) in GC patients with peritoneal metastasis. Methods: Patients with advanced GC who were diagnosed as having macroscopic PM or positive peritoneal cytology by staging laparoscopy were enrolled. We introduced intraperitoneal Paclitaxel (IP-PTX) combined with S-1 plus oxaliplatin (SOX). Gastrectomy with lymph node dissection was performed as conversion surgery when the PM showed an excellent response. Results: Ninety-six patients received IP-PTX + SOX, with a median of 16 courses. The 1- and 5-year OS rates were 70.2% and 24.5%, respectively, with a mean survival time (MST) of 20.0 months. No chemotherapy-related mortality was observed. Conversion surgery was performed in 44 patients (45.8%), with a 1-year OS rate of 100%. Conclusions: Combination chemotherapy using the IP-PTX + SOX regimen is highly effective and is recommended as induction chemotherapy for patients with PM from GC. Conversion gastrectomy should be considered following an excellent response, particularly in patients with peritoneal cancer index (PCI) scores below 20.