R. Donald Harvey, PharmD, BCOP, FCCP, FHOPA, from the Winship Cancer Institute, Atlanta, GA, discusses the importance of biomarkers in immunotherapy to improve the identification of good and poor responders. Focusing on the use of PD-1 and PD-L1 as biomarkers in the treatment of non-small cell lung cancer, Dr Harvey shares insights from conversations and debates had during the 2018 Hematology/Oncology Pharmacy Association (HOPA) Annual Conference, held in Denver, CO. Dr Harvey goes on to discuss microsatellite instability and its role in the treatment of colorectal cancer, suggesting how biomarkers can be better included in clinical trials moving forward.