A comprehensive validation of PARP1 and PARP2 expression, TP53 mutation status and MSI status as predictive biomarkers of PARPi response in CRC would require a formal, well-powered clinical trial in which PARP inhibitors are administered to CRC patients—or not—on the basis of the status of the above markers in patients’ tumor. The gene discussed is PARP1; the disease is neoplasm.