biostudies-literatureUnknown17Zhang F<h4>Background</h4>The effect of claudin 18.2 (CLDN18.2) expression on the outcomes of a first-line immune checkpoint inhibitor (ICI)-containing chemotherapy (ICI-chemo) in patients with human epidermal growth factor receptor 2 (HER2)-negative, proficient mismatch repair (pMMR), and programmed death-ligand 1 (PD-L1)-expressing metastatic or recurrent gastric or gastroesophageal junction cancers (mGC/GEJC) remains unclear.<h4>Objectives</h4>We assessed the effects of CLDN18.2 expression on the outcomes of first-line ICI-containing chemotherapy in patients with HER2-negative, pMMR, and PD-L1-expressing mGC/GEJC.<h4>Patients and methods</h4>Medical records of patients with HER2-negative, pMMR, and PD-L1 combined positive score (CPS) ⩾1 unresectable/metastatic or recurrent GC/GEJC who received first-line ICI-chemo or chemotherapy alone (chemo-alone) between January 2016 and August 2024 were retrospectively analyzed. The impact of CLDN18.2 status on the clinical outcomes was evaluated in patients receiving ICI-chemo and chemo-alone to assess the prognostic significance of CLDN18.2 in the absence of ICI.<h4>Results</h4>A total of 150 patients were treated with ICI-chemo, whereas 313 patients received chemo-alone. CLDN18.2 positivity (⩾2+ in ⩾75% tumor cells) was identified in 42 patients (28.0%) in the ICI-chemo group and 94 patients (30.0%) in the chemo-alone group. There were no significant differences in the objective response rate (ORR; 68.3% vs 70.3%, <i>p</i> = 0.842), disease control rate (DCR; 92.7% vs 94.1%, <i>p</i> = 0.718), progression-free survival (PFS; hazard ratio (HR) 1.01, <i>p</i> = 0.955), or overall survival (OS; HR 1.12, <i>p</i> = 0.615) between CLDN18.2-positive and CLDN18.2-negative patients in the ICI-chemo group. Similarly, the DCR, ORR, PFS, and OS outcomes were comparable between the CLDN18.2-positive and -negative patients in the chemo-alone group.<h4>Conclusion</h4>CLDN18.2 expression exerted no impact on outcomes of first-line ICI-chemo and chemo-alone in patients with HER2-negative, pMMR, and PD-L1 CPS ⩾1 mGC/GEJC.Therapeutic advances in medical oncology17588359251369042https://www.ebi.ac.uk/biostudies/studies/S-EPMC12450271biostudies-literatureImpact of claudin 18.2 expression on treatment outcomes of first-line immunochemotherapy in patients with HER2-negative, proficient MMR, PD-L1 CPS ⩾1 metastatic gastric/gastroesophageal junction cancer.PMC12450271Miyashita YZhang FYamamoto KNakayama IUshiyama SKojima TKawazoe ASakamoto NShitara KOkemoto DMatsubara YOkazaki UMishima SKobayashi ASato SHashimoto TJubashi AKuboki YNakamura YKotani DKuwata TBando HYoshino TfalseImpact of claudin 18.2 expression on treatment outcomes of first-line immunochemotherapy in patients with HER2-negative, proficient MMR, PD-L1 CPS ⩾1 metastatic gastric/gastroesophageal junction cancer.<h4>Background</h4>The effect of claudin 18.2 (CLDN18.2) expression on the outcomes of a first-line immune checkpoint inhibitor (ICI)-containing chemotherapy (ICI-chemo) in patients with human epidermal growth factor receptor 2 (HER2)-negative, proficient mismatch repair (pMMR), and programmed death-ligand 1 (PD-L1)-expressing metastatic or recurrent gastric or gastroesophageal junction cancers (mGC/GEJC) remains unclear.<h4>Objectives</h4>We assessed the effects of CLDN18.2 expression on the outcomes of first-line ICI-containing chemotherapy in patients with HER2-negative, pMMR, and PD-L1-expressing mGC/GEJC.<h4>Patients and methods</h4>Medical records of patients with HER2-negative, pMMR, and PD-L1 combined positive score (CPS) ⩾1 unresectable/metastatic or recurrent GC/GEJC who received first-line ICI-chemo or chemotherapy alone (chemo-alone) between January 2016 and August 2024 were retrospectively analyzed. The impact of CLDN18.2 status on the clinical outcomes was evaluated in patients receiving ICI-chemo and chemo-alone to assess the prognostic significance of CLDN18.2 in the absence of ICI.<h4>Results</h4>A total of 150 patients were treated with ICI-chemo, whereas 313 patients received chemo-alone. CLDN18.2 positivity (⩾2+ in ⩾75% tumor cells) was identified in 42 patients (28.0%) in the ICI-chemo group and 94 patients (30.0%) in the chemo-alone group. There were no significant differences in the objective response rate (ORR; 68.3% vs 70.3%, <i>p</i> = 0.842), disease control rate (DCR; 92.7% vs 94.1%, <i>p</i> = 0.718), progression-free survival (PFS; hazard ratio (HR) 1.01, <i>p</i> = 0.955), or overall survival (OS; HR 1.12, <i>p</i> = 0.615) between CLDN18.2-positive and CLDN18.2-negative patients in the ICI-chemo group. Similarly, the DCR, ORR, PFS, and OS outcomes were comparable between the CLDN18.2-positive and -negative patients in the chemo-alone group.<h4>Conclusion</h4>CLDN18.2 expression exerted no impact on outcomes of first-line ICI-chemo and chemo-alone in patients with HER2-negative, pMMR, and PD-L1 CPS ⩾1 mGC/GEJC.2025-01-01T00:00:00Z20252026-06-03T17:17:30.72Z2026-04-29T03:12:45.063ZS-EPMC124502714098504110.1177/17588359251369042