# A Mucosal Change like Hypertrophic Gastritis Following Zolbetuximab-Based Therapy in a Conversion Surgery Case of Advanced Gastric Cancer

## TL;DR

A patient with advanced gastric cancer showed mucosal changes resembling hypertrophic gastritis after zolbetuximab treatment, which may explain the observed hypoalbuminemia.

## Contribution

This is the first pathological documentation of hypertrophic gastritis associated with zolbetuximab therapy.

## Key findings

- Zolbetuximab therapy was associated with histopathological changes resembling hypertrophic gastritis.
- Hypoalbuminemia may result from zolbetuximab-induced mucosal alterations and increased protein loss.
- Tumor regression enabled conversion surgery, highlighting the potential of zolbetuximab in advanced gastric cancer.

## Abstract

Background and Clinical Significance: Zolbetuximab, a claudin 18.2-targeted monoclonal antibody, has demonstrated efficacy in advanced gastric cancer. Hypoalbuminemia has emerged as a notable adverse effect, but its underlying mechanism remains unclear. Case Presentation: A 53-year-old male with unresectable advanced gastric cancer received zolbetuximab-based combination therapy, achieving tumor regression enabling conversion surgery. During six cycles of treatment, serum albumin levels decreased from 4.3 g/dL to 3.5-3.6 g/dL (grade 1 hypoalbuminemia). A histopathological examination of the surgical specimen revealed hypertrophic gastritis characterized by marked foveolar hyperplasia, increased mucus secretion, and pyloric gland metaplasia on the lesser curvature. These findings suggest that zolbetuximab-induced mucosal alterations may contribute to hypoalbuminemia through enhanced protein loss. Conclusions: This is the first pathological documentation of hypertrophic gastritis associated with zolbetuximab therapy. Clinicians should monitor albumin levels during treatment and consider nutritional support when indicated. These findings provide important insights for optimizing patient management and ensuring safe conversion surgery planning.