Abstract 3730: Impact of proton pump inhibitor on ICI with or without chemotherapy for NSCLC with high PD-L1 TPS

Abstract Background and Aim: Immune checkpoint inhibitors (ICIs) have been widely used for the initial treatment of non-small cell lung cancer (NSCLC). Although both ICI monotherapy and the combination of ICI plus chemotherapy (chemo-ICI) are promising therapeutic options for patients with a programmed cell death ligand-1 tumor proportion score of 50% or higher (high PD-L1), the patient's clinical background and biomarkers differentiating the two options are still not well-defined. In our prior research, we found that a history of proton pump inhibitor (PPI) use independently have negative impact with significantly shorter overall survival (OS) and progression-free survival (PFS) in NSCLC patients harboring high PD-L1 with pembrolizumab monotherapy, but not with chemo-ICI. However, this OS data remain immature. Therefore, in our current study, we extended the follow-up period and conduct additional analysis including OS data to confirm this trend. Method: Advanced NSCLC patients with high PD-L1 who had received pembrolizumab or chemo-ICI as the first-line treatment between March 2017 and December 2020 at 13 hospitals in Japan were analyzed. Survival outcomes were estimated using the Kaplan- Meier method and were compared using the log-rank test. Results: A total of 425 patients with NSCLC were included in the study, with 271 patients (median [range] age, 72 [43-90] years; 215 [79%] men) receiving pembrolizumab monotherapy as their first-line treatment and 154 patients (median [range] age, 69 [36-86] years; 121 [79%] men) receiving chemo-ICI as their first-line treatment. The median follow-up duration was 22.8 months. Among patients with a history of PPI use, both median PFS (19.3 months vs. 6.8 months; HR, 0.53; 95% CI, 0.35-0.78; P = .003) and the median OS(not reached vs. 20.4 months; HR, 0.53; 95% CI, 0.34-0.85; P = .04) were significantly longer in the chemo-ICI group compared to the pembrolizumab monotherapy group. For patients without a history of PPI use, both median PFS (11.4 months vs. 10.8 months; HR, 0.99; 95% CI, 0.76-1.3; P = .36) and the median overall survival (42.2 months vs. 29.9 months, HR, 0.84; 95% CI, 0.62-1.16; P = .33) showed no significant differences between the groups. Discussion and Conclusion: This retrospective study showed that a concomitant treatment with PPI is poor prognostic factor in patients harboring high PD-L1 and treated with ICI monotherapy compared with chemo-ICI in Japanese cohort and this tendency is durable in long-term follow-up. These results indicate that when deciding on an ICI treatment, with or without chemotherapy, it is essential to take into account a concomitant treatment with PPI. Citation Format: Ryo Sawada, Hayato Kawachi, Tadaaki Yamada, Motohiro Tamiya, Yoshiki Negi, Yasuhiro Goto, Akira Nakao, Shinsuke Shiotsu, Takayuki Takeda, Asuka Okada, Taishi Harada, Koji Date, Yusuke Chihara, Isao Hasegawa, Takashi Kijima, Koichi Takayama. Impact of proton pump inhibitor on ICI with or without chemotherapy for NSCLC with high PD-L1 TPS [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3730.