Gallbladder edema as a clue to zolbetuximab-associated protein-losing enteropathy in gastric cancer: a case report.

We report a rare case of protein-losing enteropathy (PLE) during zolbetuximab treatment in a 73-year-old woman with Stage IVB gastric cancer. After chemo-immunotherapy and curative surgery, 3rd-line treatment with capecitabine, oxaliplatin, and zolbetuximab was initiated due to recurrence. The patient developed persistent right upper abdominal pain; imaging revealed gallbladder wall edema, followed by mild gastric wall edema, despite unremarkable laboratory findings. Protein-losing scintigraphy demonstrated abnormal gastric protein leakage, leading to a diagnosis of PLE. While gastrointestinal toxicity is known with zolbetuximab, this is, to our knowledge, the first clinically diagnosed case of PLE in which gallbladder edema served as a diagnostic clue. As treatment strategies for advanced gastric cancer grow increasingly complex, achieving maximum therapeutic benefit requires not only optimal drug selection but also timely recognition and management of adverse events. With the broader use of zolbetuximab, clinicians should be mindful of this rare but potentially significant complication.