Efficacy of immune checkpoint inhibitors in microsatellite unstable/mismatch repair-deficient advanced pancreatic adenocarcinoma: an AGEO European Cohort.

Background: Immune checkpoint inhibitors (ICIs) improve oncological outcomes in patients with microsatellite instability-high (MSI) or mismatch repair-deficient (dMMR) advanced solid tumours. Nevertheless, based on limited published data, the outcome of patients with MSI/dMMR pancreatic ductal adenocarcinoma (PDAC) seems poorer when compared to other malignancies. This multi-institutional analysis sought to assess the efficacy and tolerability of ICIs in a large real-world cohort of patients with MSI/dMMR PDAC.

Methods: We retrospectively collected data from patients with MSI/dMMR advanced PDAC treated with ICIs in 16 centers. Progression-free survival and overall survival were calculated from the start of treatment, and we report objective response and disease control rates according to RECIST V1.1.

Results: Thirty-one MSI/dMMR advanced PDAC patients were identified. Twenty-five patients received single-agent anti-PD-1 antibodies, three patients received the combination of nivolumab and ipilimumab and three patients received immunotherapy in combination with chemotherapy. Among 31 evaluable patients, 15 (48.4%) had an objective response (three complete responses and 12 partial responses), and six (19.4%) had stable disease. With a median follow-up of 18 months, the median progression-free survival (PFS) was 26.7 months and the median overall survival (OS) was not reached. Disease control rates (DCRs) among patients with only one line of prior therapy (N = 17) was 76.5%. Grade 3-4 treatment-related adverse events were not observed.

Conclusion: This retrospective analysis suggests that ICIs are effective and well tolerated in patients with MSI/dMMR advanced PDAC. Hence, our work supports the use of PD-1 inhibition in this group of patients with high unmet medical need.