KEYNOTE-158-MSIH

NCT02628067 📎

Regimen

Experimental
Pembrolizumab 200 mg IV q21d for up to 35 cycles (2 years)
Control
single-arm / no comparator

Population

MSI-H or dMMR advanced non-colorectal solid tumors after ≥1 prior therapy across 10 tumor cohorts; Cohort K = biliary tract cancer (n=22 of 233 total BTC in MSI-H analysis; MSI-H prevalence in BTC ~2-3%). Primary pub: Marabelle A, JCO 2020 (PMID 31682550) — reports overall non-CRC MSI-H ORR and tumor-cohort breakdown. Long-term update: Maio M, Ann Oncol 2022 (PMID 35680043) — extended follow-up. BTC cohort: predominantly ICC; MSI-H detected by PCR or NGS.

Key finding

KEYNOTE-158 Cohort K provided the BTC-specific MSI-H efficacy data that contributed to the pan-tumor FDA accelerated approval of pembrolizumab for MSI-H/dMMR solid tumors (June 2020). The BTC cohort ORR of 40.9% (n=22) is limited by small sample size but directionally consistent with pembrolizumab activity across MSI-H tumor types. The Maio 2022 Ann Oncol update (PMID 35680043) extended follow-up and confirmed durable responses in MSI-H responders regardless of histology. MSI-H prevalence in BTC is ~2-3%, making universal MSI testing in BTC critical for a small but potentially highly responsive subgroup.

Source: PMID 31682550

Timeline

    Guideline citations

    • NCCN BTC (p.34)