Here we presented a case of advanced iCCA that responded dramatically to the PD-1 inhibitor sintilimab combined with GC regimen as first-line systemic therapy....Within the first 2 months of treatment, CT results showed that the tumor size was decreased from 83 mm × 72 mm to 64 mm × 64 mm (Figures 1A, B). Then the tumor had shrunk gradually. In May 2020, CT results showed that the huge tumor had shrunk to 22.5% of the size before treatment (Figure 1C)....In this case, the patient had an ARID1A mutation and reached a PFS of 16 months, which suggested that ARID1A mutation might be a potential biomarker for ICIs in iCCA, regardless of MSI, PD-L1, or TMB status.

After eight cycles of treatment, the combination of sintilimab and capecitabine was administered as maintenance therapy. The tumor lesions disappeared completely, and the patient had a long-term benefit….To date, there is no further enlargement of the primary tumor (Figure 1D). The metastases had disappeared entirely. The progression-free survival (PFS) has already exceeded 16 months....In this case, the patient had an ARID1A mutation and reached a PFS of 16 months, which suggested that ARID1A mutation might be a potential biomarker for ICIs in iCCA, regardless of MSI, PD-L1, or TMB status.