Dr. Chao on the Utility of MSI as a Biomarker in Gastric/GEJ Cancer

Partner | Cancer Centers | <b>City of Hope</b>

Joseph Chao, MD, discusses the utility of microsatellite instability (MSI) status as a prognostic biomarker in gastric and gastroesophageal cancer.

Joseph Chao, MD, assistant clinical professor, Department of Medical Oncology and Therapeutics Research, City of Hope, discusses the utility of microsatellite instability (MSI) status as a prognostic biomarker in gastric and gastroesophageal junction (GEJ) cancer.

Typically, patients with stage IV gastric/GEJ cancer have a relatively poor prognosis, says Chao. However, MSI—high (MSI-H) patients have improved outcomes with PD-1 inhibitors.

In September 2017, the FDA approved the PD-1 inhibitor pembrolizumab (Keytruda) for the treatment patients with PD-L1—positive recurrent or advanced gastric/GEJ adenocarcinoma who have received ≥2 prior lines of therapy.

A comparative analysis of the phase II KEYNOTE-059 and phase III KEYNOTE-061 and KEYNOTE-062 trials indicated that pembrolizumab monotherapy elicited clinically meaningful efficacy and more durable responses compared with chemotherapy in patients with a combined positive score ≥10 in the first-, second-, and third-line settings.

In Japan, regulatory authorities approved nivolumab (Opdivo) for patients with gastric/GEJ cancer regardless of biomarker status. However, MSI-H patients who receive nivolumab derive favorable outcomes compared with patients with microsatellite stable disease, concludes Chao.