The primary objective is to validate, throughout a national real-world study, the efficacy and safety of Zolbetuximab combined with FOLFOX or XELOX regimens. Specific clinical issues will be studied by pre-planned subgroup analyses, addressing practical clinical needs which have not been specifically investigated in randomized clinical trials.

Advanced HER-2 negative gastric adenocarcinoma and gastroesophageal junction adenocarcinoma represents an oncological entity with a relatively poor prognosis and limited therapeutic options. Zolbetuximab, marketed as VYLOY, is a monoclonal antibody targeting the Claudin 18.2 protein, a tissue marker highly expressed in around 30 to 40% of GA or GEJA adenocarcinomas.

On September 20, 2024, the European Medicines Agency approved the use of VYLOY (zolbetuximab) in combination with fluoropyrimidine- and platinum-based chemotherapies as a first-line treatment for adult patients with locally advanced unresectable or metastatic HER2-negative and Claudin 18.2 positive gastric or gastroesophageal junction adenocarcinoma.

This approval is based on two positive phase III randomized clinical trials, SPOTLIGHT and GLOW, which demonstrated the efficacy of Zolbetuximab in this clinical context.

In October 2024, following this approval, an Early Access Program (EAP) was launched in Italy to provide early access to eligible patients for this treatment. (ClinicalTrials.gov ID NCT06048081) This national-scale prospective real-world observational study aims to validate the efficacy and safety data of zolbetuximab in combination with fluoropyrimidine- and platinum-based chemotherapies, analyzing specific clinical aspects through pre-planned subgroup analyses.

Inclusion Criteria:

• Patient with histologically confirmed diagnosis of gastric or gastroesophageal junction adenocarcinoma.
• Patient with locally advanced, unresectable or metastatic gastric or gastroesophageal junction adenocarcinoma.
• Patient whose tumor expresses claudin18.2 in ≥ 75% of tumor cells demonstrating moderate to strong membranous CLDN18 staining as determined by local or central immunohistochemistry testing.
• Patient with a Human epidermal growth factor receptor 2 negative tumor by local testing on a gastric or gastroesophageal junction tumor specimen.
• Patient with Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1.
• Patient who can have access to the Zolbetuximab EAP program or locally authorized and reimbursed (AIFA) procedure.
• Patient who has about to start first-line Zolbetuximab + FOLFOX/XELOX or who has an ongoing Zolbetuximab FOLFOX/XELOX with available clinical data.

Exclusion Criteria:

• Patient has previously received treatment in a clinical trial of zolbetuximab, or a clinical trial that included zolbetuximab as 1 of the treatment options, even if the patient was not given zolbetuximab.
• Patient has known dihydropyrimidine dehydrogenase deficiency.
• Patient has received prior systemic chemotherapy for locally advanced unresectable or metastatic gastric or gastroesophageal junction adenocarcinoma. However, patient may have received either neoadjuvant or adjuvant chemotherapy, immunotherapy or other systemic anticancer therapies as long as it was completed at least 6 months prior to participation.

Adult patients (≥ 18 years) with advanced HER-2 negative and Claudin 18.2 positive gastric or gastroesophageal junction adenocarcinoma.