The HRD mutational signature (SBS3) is enriched in brain metastases from colorectal cancer14, has been detected in primary and metastatic PCa, independent of BRCA1/2 alterations15 and has been suggested to contribute to the accurate prediction of response to PARP-inhibitor treatment in combination with the presence of alterations affecting HRR genes16. The gene discussed is BRCA1; the disease is posterior cortical atrophy.