Solid tumors represent approximately 90% of adult human cancers. They can develop in many parts of the human body, including the breast, lung, prostate, colon, melanoma, bladder, and kidney. Normal cells have a system that sees and repairs mistakes that happen when the DNA is copied. It’s called the mismatch repair system. Sometimes the system stops working properly. When this happens, errors in the DNA start accumulating and may cause cancer.

DNA mismatch repair (MMR) is a process that plays a key role in maintaining genomic stability by recognizing and repairing base-base mismatches and insertion/deletion of DNA generated during replication and recombination. Defects in MMR are associated with genome-wide instability and the progressive accumulation of mutations, especially regions of simple repetitive DNA sequences known as microsatellites, resulting in MSI.

In an ESMO session titled “Biomarkers for cancer immunotherapy", experts discussed how patients with dMMR/MSI-H tumors can benefit from immunotherapy. Chaired by Prof. Thierry Andre’, the session saw participation from Dr. Anna Tinker, University of British Columbia Vancouver, Canada, and Prof. Josef Ruschoff Targos, Molecular Pathology GmbH Kassel, Germany.