BRCA1 and hypoparathyroidism-retardation-dysmorphism syndrome: Studies have shown that mutations in genes such as BRCA1, BRCA2, PALB2 and ATM cause homologous repair deficiency (HRD), with HRD reaching 14.5-16.5% in patients with PDAC 60, 61.HRD affects DNA double-strand break repair and increases sensitivity to poly ADP-ribose polymerase (PARP) inhibitors.