Genomic characterization and immunotherapy for microsatellite instability-high in cholangiocarcinoma

BACKGROUND

Microsatellite instability-high (MSI-H) is a unique genomic status in many cancers. However, its role in the genomic features and immunotherapy in cholangiocarcinoma (CCA) is unclear. This study aimed to systematically investigate the genomic characterization and immunotherapy efficacy of MSI-H patients with CCA.

METHODS

We enrolled 887 patients with CCA in this study. Tumor samples were collected for next-generation sequencing. Differences in genomic alterations between the MSI-H and microsatellite stability (MSS) groups were analyzed. We also investigated the survival of PD-1 inhibitor-based immunotherapy between two groups of 139 patients with advanced CCA.

RESULTS

Differential genetic alterations between the MSI-H and MSS groups included mutations in ARID1A, ACVR2A, TGFBR2, KMT2D, RNF43, and PBRM1 which were enriched in MSI-H groups. Patients with an MSI-H status have a significantly higher tumor mutation burden (TMB) (median 41.7 vs. 3.1 muts/Mb, P < 0.001) and more positive programmed death ligand 1 (PD-L1) expression (37.5% vs. 11.9%, P < 0.001) than those with an MSS status. Among patients receiving PD-1 inhibitor-based therapy, those with MSI-H had a longer median overall survival (OS, hazard ratio (HR) = 0.17, P = 0.001) and progression-free survival (PFS, HR = 0.14, P < 0.001) than patients with MSS. Integrating MSI-H and PD-L1 expression status (combined positive score ≥ 5) could distinguish the efficacy of immunotherapy.

CONCLUSIONS

MSI-H status was associated with a higher TMB value and more positive PD-L1 expression in CCA tumors. Moreover, in patients with advanced CCA who received PD-1 inhibitor-based immunotherapy, MSI-H and positive PD-L1 expression were associated with improved both OS and PFS.

TRIAL REGISTRATION

This study was registered on ClinicalTrials.gov on 07/01/2017 (NCT03892577).

Are targeted therapies or immunotherapies effective in metastatic pancreatic adenocarcinoma?

Metastatic pancreatic ductal adenocarcinoma (PDAC) is a major health burden due to its increasing incidence and poor prognosis. PDAC is characterized by a low tumor mutational burden, and its molecular pathogenesis is driven by Kirsten rat sarcoma viral oncogene homolog (KRAS) mutations. Response to DNA damage through homologous repair is defective in 15% of tumors. Chemotherapy using FOLFIRINOX (folinic acid, fluorouracil, irinotecan, oxaliplatin) or gemcitabine-nab-paclitaxel significantly improves life expectancy, but the median overall survival remains <1 year. Targeted therapies are not efficient in the overall population of patients with metastatic PDAC. Improvements in overall survival or progression-free survival, however, have been demonstrated in subgroups carrying certain mutations. Maintenance therapy with poly-ADP-ribose polymerase (PARP) inhibitors increases progression-free survival in patients with germline mutations in BRCA1/2. Sotorasib shows signs of efficacy against tumors carrying the KRAS G12C mutation, and targeted therapies may also benefit patients with KRAS-wild-type PDAC. Combining targeted therapies with chemotherapy holds promise because of potential synergistic effects. These associations, however, have not yet demonstrated clinical benefit. Checkpoint inhibitors are not effective against metastatic PDAC. Combined immunotherapies attempt to restore their efficacy but have not succeeded yet. Other immunotherapies are emerging such as therapeutic vaccines or chimeric antigen receptor (CAR) T cells, but these strategies remain to be evaluated in large trials. In the future, treatment personalization based on tumor-derived organoids could potentially further improve treatment efficiency.