Impact of prior nivolumab use on the efficacy of second-line taxane-based chemotherapy in advanced gastric or esophagogastric junction adenocarcinoma.

352 Background: Taxane-based chemotherapy remains the standard second-line treatment after first-line treatment including anti-PD-1 antibody therapy for patients with advanced gastric or esophagogastric junction adenocarcinoma (GA/EGA). The CheckMate 649 trial suggested that prior use of nivolumab in the first-line setting was associated with longer progression-free survival (PFS) with subsequent treatment. However, there have been few reports on the difference in efficacy of taxane-based chemotherapy as second-line treatment with or without prior nivolumab use in the real-world setting. Methods: We retrospectively reviewed the medical records of patients with advanced GA/EGA who received solvent-based paclitaxel or nanoparticle albumin–bound (nab)-paclitaxel chemotherapy regimens as second-line treatment after first-line platinum-based chemotherapy between January 2018 and August 2024. We divided the patients into two groups: those who received nivolumab with the first-line chemotherapy (Nivo group) and those who did not (non-Nivo group). PFS and overall survival (OS) were estimated using the Kaplan–Meier method and compared between the two groups using the log-rank test. Hazard ratios (HRs) and 95% confidence intervals (95%CIs) were estimated by univariate and multivariate Cox regression analysis. Results: A total of 115 patients were included: 27 patients in the Nivo group and 88 in the non-Nivo group. Patient backgrounds did not differ significantly in terms of age (median 67/67 years), sex (male 59%/57%), performance status (PS; ≥2 11%/15%), site of primary tumor (EGA 11%/9%), number of metastatic sites (≥3 33%/18%), and ramucirumab use (yes 82%/82%). For the taxane regimens, nab-paclitaxel-based treatment was significantly more common in the non-Nivo group (11.1% /55.7%, p<0.001). There was a tendency toward longer PFS in the Nivo group compared with the non-Nivo group (median 4.2 months [95%CI 2.8-6.0] vs. 2.3 months [95%CI 2.0-3.0], HR 0.65 [95%CI 0.40-1.03]; p=0.067.) The objective response rate was numerically higher in the Nivo group compared with the non-Nivo group (29.4% vs. 17.6%, p=0.315). OS was not significantly different between the Nivo and non-Nivo groups (median 9.6 months [95%CI 4.9-NA] vs. 6.6 months [95%CI 5.5-10.8], HR 0.92 [95%CI 0.52-1.64]; p=0.785). In the non-Nivo group, 64 patients (73%) received subsequent chemotherapy, and 63 patients (72%) received nivolumab. Multivariate analysis identified prior use of nivolumab was a favorable prognostic factor for PFS (HR 0.55 [95%CI 0.31-0.97]; p=0.039). However, prior use of nivolumab did not show a significant benefit for OS (HR 1.09 [95% CI: 0.56-2.13]; p = 0.802). Conclusions: Prior use of nivolumab in first-line platinum-based chemotherapy had a positive impact on PFS with taxane-based second-line chemotherapy in advanced GA/EGA.