Tumor programmed death ligand 1 (PD-L1) expression evaluated by immunohistochemical (IHC) stains and mismatch repair (MMR) deficiency examined by IHC stains of the MLH1, MSH2, MSH6 and PMS2 expression or by microsatellite instability assay are currently used to select patients for immune checkpoint therapy. Tumor mutational burden (TMB) is an emerging marker to predict outcomes of immune checkpoint therapy in a variety of solid tumors (PMID: 29658845; PMID: 30123559). Further studies, however, are needed to standardize the TMB assays and to define the threshold for clinical significant TMB.
In August 2018, the Molecular Diagnostics Lab is introducing a Tumor Mutation Rate calculation for the “large” Solid Tumor Sequencing Panels (STP-2). This calculation was derived based on the Foundation One Tumor Mutation Burden calculation.