Genomic and biomarker analysis of immunotherapy combined with chemotherapy treated for patients with metastatic BTC cancer: A real world study.

e16373 Background: Biliary tract cancer (BTC) is a heterogeneous group of diseases with dismal prognosis. The TOPAZ-1 phase III trial and KENOTE 966 reported a survival benefit with the immune checkpoint inhibitor (ICI) plus chemotherapy (GemCis,GC) in patients with advanced BTC. Consequently, immunotherapy plus chemotherapy has become a new standard care for advanced BTC. Understanding the association between genomic alterations and immunotherapy outcomes of BTC could further improve the clinical benefits. Therefore, we conducted this real-world study in China. Methods: This study included 47 patients with metastatic BTC treated with PD-1/PD-L1(ICI) antibodies in combination with chemotherapy from January 2019 to January 2023 in Medical Oncology department of Chinese PLA General Hospital. The primary endpoint was progression-free survival (PFS). The secondary endpoints included overall response rate (ORR), disease control rate (DCR). The exploration endpoint was genomic and biomarker analysis. Genomic tumor DNA was isolated from 30 patients and used for targeted next-generation sequencing genes to identify the genomic profiles. Results: 47 patients received immune checkpoint inhibitor (ICI) plus with chemotherapy in first line were enrolled in this study. The median PFS were 5.4m (95%CI,4.4-6.3), ORR and DCR was 21.3% and 83.0%, respectively. Patients were grouped into two group:AS+PD1(n=34) group and GC+ICI(n=13) group. In the AS(Albumin paclitaxel+S1)+PD1 group, mPFS was 5.0m (95%CI 3.8-6.1), ORR were 20.6% and DCR were 79.4% as we reported previously. In the GC+ ICI, mPFS was 7.9m (95%CI 4.7-11.1), ORR was 23.1% and DCR was 92.3%. There was no difference in terms of PFS, ORR and DCR between two groups. With regard to biomarker analysis, PD-L1 expression positive were 16 patients, which of mPFS were 4.2m and ORR were 18.8%, otherwise 12 patients were PDL1 expression negative, of whom mPFS were 9.1m and 33.3% as unexpected. Average TMB were 4.5mt/MB for MSS type patients. There is no difference of PFS between TMB high(>4.5mt/MB) or low(5.4m)and short term survival(PFS<5.4m), MDM2 was only predictor for short survival(p<0.05). Conclusions: Compared to AS+pd-1, patients received GP+ ICI numerically had better outcomes. It seems PD-L1 and TMB were not good predictors to select patients who can more benefit from immunotherapy plus chemotherapy. MDM2 mutation suggest patients tend to less active to immunotherapy-based modality.